There is no soft-balling going on. Once again, already done status-quo DMing
No need to get defensive. Not status quo doesn't mean soft-balling. It can mean going full bore killer DM. Or, as I assume you're going for in your case, creating a challenging encounter for the party.
It does not work for my group. If I just toss out some guys I dreamed up without taking into account the party's capabilities, the party will wipe them out.
That doesn't necessarily follow. If you dream up Asmodeus and his arch-devils having a tea party in the dungeon, and your 1st level party blunders into them, I doubt it'll go that way. ;P I don't know why the status quo would include dukes of hell hanging out under a ruined guard tower in an out-of-the-way township, but if it did, oh well, don't go in that dungeon again until your new characters are much higher level.
The disconnect is happening because Hemlock has interpreted "challenging the party without killing them" as "not trying to kill them." This is not correct. The idea behind challenging a party without killing them has to do with encounter creation and has nothing to do with intent. The enemies are always trying to kill the PCs unless they have some alternative goal like imprisonment or slavery.
I don't think anyone was suggesting that the DMs intent in creating an encounter, whether tailored or status quo, changed the intent of the creatures making up that encounter. For one thing, they're imaginary: strictly speaking, they have no intent. For another, a tailored encounter meant to be a roll-over for the party could consist of outmatched, but overconfident, monsters none-the-less determined to kill the party. Conversely, I suppose, you could have a lethal encounter with a bumbling young StormGiant who 'doesn't no his own strength' ("whoops, sorry 'bout crushing your buddy, little guy..."). Intent of the monsters has nothing to do with it, just intent of the DM.
Your intent is clearly to challenge your players and thus run a game session that doesn't suck for everyone at the table. Perfectly reasonable.
Hemlock's intent is probably to create an imagined world that is typical of a certain fantasy sub-genre, and, while the genre might typically revolve around a hero(es) who improbably win through deadly danger after deadly danger, the party is just going to have to deal with survival in such a world with nothing but dice luck and 'player skill' to see them through - no artistic license from the author is going to help or hinder them.
You can each adapt 5e to those purposes. I suppose you might have a little more work to do in that regard than he.
I'm pretty sure you've been doing this long enough to have had similar experiences where you are designing an encounter. You think the encounter is damn cool. You think the party can handle it. Then you run the encounter, they end up getting pasted. Then you have this group of pissed off players that feel you screwed them, especially if you designed the encounter in such a fashion they had zero chance of winning. You didn't realize this would happen until you killed the party.
Happens all the time - more the less well-balanced the game, and less dependable it's encounter guidelines. Classic D&D, for instance, not well balanced at all, and no encounter guidelines to speak of. Kinda a long learning curve, but a lot of us stuck with it.
I don't get how Hemlock doesn't get what I'm talking about. To me this is easy to understand. If some of the more experienced DMs told me the same concept, I'd understand immediately what they were talking about. I wouldn't refer to it as soft-ballling or "trying to protect the party." I'd say, "Oh experienced DM. He has probably killed the party a ton and dealt with the unhappy after effects."
Soft-balling or over-killing or challenging - it's all the same in the eyes of an old-school DM. You're basing the encounter on the party. You may be justly proud of doing so /well/ - which has rarely been easy in a game like D&D - and thus consistently producing challenging encounters, but Hemlock may well be indifferent to that distinction.