Is setting up difficult challenges "playing against the player?"
Typically, yes, especially if you consider the abilities of the PCs before the storyline when creating the challenges.
When I create a game, I come up with story first. If there is a lich that has a MacGuffin, I ask where he got it, why he has it, and what he intends to do with it. Then I ask if he'd want to protect it. If so, what resources might he have to protect it. I craft that story, adding story elements and challenges to the tale and ONLY consider the PCs if the monster would consider those PCs. If the lich knows the PCs are coming and has time to prepare for it, he'll tailor the defenses to them. If not, I don't factor in their abilities at all (subject to the slight cheat that if they have abilities that are likely to bypass his defenses, I don't flesh out those defenses too much.
How do the PCs fit into this planning? Often, I use the goals or focuses of the party as inspiration for where to begin this construction. If the PC wizard has a goal to obtain the Staff of the Magi, I figure out where that staff is ASAP and then create a path to it - but the challenges along the way are not tailored to that PC (or the party in general. The PCs inspire, but they are not part of the calculations and machinations.
Am I not "creating for" the players when I present challenges of the difficulty level they prefer?
Not in the way I mean it. You're setting up a strategy game, but not really creating a deep world for their adventuring pleasure. You're focused on strategy over story.
Might I suggest an exercise: Try building a session worth of encounters that is fun for your group, but where no encounter is more than "medium" difficulty per the DMG standards. How can you challenge PCs without threatening their lives? I've faced a lot of serious challenges in my (real world life), but my life has only been in jeopardy a couple times.
I don't really know what you mean by "support(ing) player decisions."
I mean looking at what your players are trying to do and allowing them to have success where they put in the focus. Notice: I did not say you were tailoring the game to their strengths... I said allowing them to have success. That means not gaming against their strengths, but instead creating fun encounters agnostic to their strengths and weaknesses (unless there is a story reason why an encounter would be tailored to their abilities) so that they can use the strengths they invested in obtaining.
But have I said anything that would lead you to believe I don't support them?
I do see something in your language. That is why I focused on your language in the prior post. You're apparently not seeing it the same way, however.Often, setting up difficult challenges for the PCs is playing against them. "Setting up" heavily implies you are looking at their abilities and trying to play against them. You don't need to do this to create a fun game and doing it diminishes the player choices by negating what they want to do. See my prior statements for more on this idea.
I think by definition choices I make are my choices.
To an extent, clearly. But what else are they?
And again, I refer to you previous posts in which I address the issue of "what monsters and NPCs would choose." They choose whatever I make them choose because they are under my complete control. And if I want to have them do a thing that maintains a certain level of difficulty, overcoming which gives a great sense of achievement to the players, then I can easily make up an acceptable fictional reason for why they do that. Fiction is great that way.
This is the crux: Does the story influence the strategy, or the strategy influence the story? Which is better? Is it s ROLE PLAYING game or a role playing GAME.
If you go with the rpG, you're making a mistake. Why? Because there are a lot of better games out there for pure strategic fun. Boradgamegeek can point you to thousands of hours of amazing games. I can give you a lot of suggestions, too - including Gloomhaven. If you have not checked it out, you should.
If you go with RPg, then you don't want to be justifying your monster decisions so that they can make choices that are harder for the PCs. You want the story to guide the strategy. You want the monsters to (often) make suboptimal combat decisions because it is more interesting for them to be serving their non-combat/opposing goals, or because they just don't have the mental capacity to make the optimal choice.
Think about it this way: A lot of people really love published adventures. Why? They're not tailored to the PCs. The challenges in them are written with no concern to the actual party that will undertake the adventure.
When people talk about playing Castle Ravenloft, the idea of a Dragonborn Wild Sorcerer Hermit is not the first thing that leaps to my mind. The challenges of the adventure are not crafted to that PC type...
...but that is what makes it fun for that PC to venture into that adventure. They bring something... unexpected? ... to the game. The bad guys are not prepared for her unique capabilities. That tells a great story.
We don't need to metagame - and that is the right word (making choices based upon their game statistics rather than based upon the story) - against the PCs to make a good game, and metagaming against them often frustrates them.
YMMV. You may play at a table where the PCs really just care about strategy games and want you to focus only on what would be a good challenge at the table. They may tune out the second combat ends and tune back in only when combat begins, asking, "So what are we fighting? I missed everything the DM said in the last 30 minutes... there was a Giggazorasaurus nearby and I was trying to catch it with my Pokeballs because I just got a bunch of dust." If so, you can continue focusing on being their opposition and maintain the status quo... but I encourage you to try my way with them for a few weeks. You might find that they tune out less in the time between combats and that you're all having even more fun. I've seen this turn in many groups over the decades... I speak from experience. Just trying to help. Hopefully, food for thought.