They matter to everyone. So, let’s talk about other factors.
No one has responded to this yet so please look at the two descriptions below.
(1) A character faces a cliff that he needs to climb. The GM checks his notes and sees that the cliff is not very detailed other than a basic description and a climb DC. He has to make a ruling! He decides that the character could conceivably and plausibly determine how difficult the climb may be, and the GM then shares all the relevant game information with the player.
(2) A character faces a cliff that he needs to climb. The GM checks his notes and sees that the cliff is not very detailed other than a basic description and a climb DC. He has to make a ruling! He decides that the character would not be able to determine the difficulty of the climb just by surveying it from his vantage point. He does not share the relevant game information with the player.
What relevant game information? This is pretty important to the example
If I am playing OSR I am fine with the GM giving me or not giving me the information so long as they are basing it on what I would see. If the GM says, it is hard to tell from here how difficult it is, I would follow up with further questions and maybe try to get a better vantage point. I wouldn't expect him to give me the information simply to be generous with info.
And while I don't base everything I do on it, the OS Primer mentions because it is a very common idea in the OSR: "Fourth Zen Moment: Forget about "Game Balance". You are expected to give them whatever information they would rightfully have. You aren't expected to give them information you don't think they would have.
The baseline assumption though in a situation like this should be it could be very challenging. A lot of OSR systems don't even have Climb skills. They are just going to be attribute rolls or something. And these are usually high lethality games.
That said, if the player can see the cliff face, they should have some idea of how difficult it looks to climb. If there is a good reason why they wouldn't be able to discern that, fair, but this example feels off for this reason to me
Given that each of these approaches has considered the plausibility of a climber knowing how tough a climb will be, what other reasons might there be for choosing option (2) over option (1)?
Again in an old school, the GM should base it on what they think the PC should know. And if the issue is the cliff hasn't been thoroughly set up in the notes, the GM should decide on the spot how hard it is, or roll to figure it out. And if the player is looking right at the cliff, they probably should be able to give them a description of it. I don't think I would tell teh player "It looks hard". I would tell them about what the cliff looks like and describe features that play a role in how challenging it is
But they are the author of what the character would know from their vantage point.
Not entirely. Because the players have been interacting with the environment the whole time. The player is is going to have a lot of say on how the cliff is approached, they are going to have a good sense of the overall layout of the area they are exploring. And again, while balance isn't a big consideration, the aim is also not to screw the players. This is why Q&A are so crucial. The players are going to be asking lots of questions as they approach so they have some say in what kind of vantage point they end up getting. Ultimately the GM will have final say, but this isn't like the GM is just decreeing everything from on high with no player input
That’s what no one is admitting. Everyone is acting like the world actually exists and is independent and exerting actual cause and effect. But the world is a bunch of decisions made by the GM. The GM makes the decision if it’s plausible for the climber to know how tough the climb will be… he can rationalize it as realistic or plausible either way he decides.
Again, we have had this conversation too many times to count. And if you won't buy one of the fundamental premises of Old school play, fair. You don't have to. But the idea is you are modeling an environment for the players to explore as if it is an objective place. The GM is not just deciding things arbitrarily. And the Q&A is a very important part of helping this process along.
So what else should he be considering?
I don;t know why you keep going back to this. He should be considering what he thinks the player can see and giving them the information they would have. And this should be open to Q&A. There can be other considerations as well. There is nothing wrong with doing this, and trying to do other things. But the GM doesn't have to do anything beyond tell them what he thinks they would see