Now it has been my general experience, gaming wise, that most Magic Users are run by players that also GM. I don't know if it's a factor of the extra "stuff" that can go into playing a Magic User, the extra details having to do with spell casting, or maybe that GMs acting as players like to be able and sit back a bit more during games (low-level Magic Users are largely strap-hangers for a long time). In some, possibly crunchier games, it can be hard to play "stupid" since you have GM knowledge and maybe running a naturally smarter PC helps. My 7th level HackMaster Double Specialist Invoker had an Intelligence of 21......and hopefully that's my one HackMaster reference for the post (doubtful).
One thing I do really enjoy in a less "crunchy" OSR game is magic in general. Since I'm sitting at someone else's table (so to speak since I'm in an online game) I might have some some assumptions about how the magical world works, but I'm constantly surprised by how another GM interprets or even tweaks their particular campaign/game wurld/rules.
For example I have a list of spells my PC already knows and they're in my spell book. Now I've gone above & beyond statting out my spellbook particulars, largely using HackMaster 4th edition rules.....because I want to. It's probably more something that my GM can handicap with in the future, but whatever. I also currently have a captured and I know what spells are in that particular book. When my PC leveled the GM had me roll up a new spell and *ding* that's a spell I now know. While he was at it he had me make a few other rolls and *ding* there were some other spells I was automagically able to figure out. The rationale was that I'd been kind-of taught these spells before, but I just couldn't "get them" until this point. Since this was an OSR game and not my all-too-often-referenced HackMaster, this was pretty much handwaved as opposed to the result of a bunch of tables after having ponied up a bunch of GP and formally sent my Enchanter off to a training school to formally level up.
Close enough to the same results but this go-around was so much less constrained and clearly simpler. The thing is I don't think I'd have done this easy hand-waving bit if our roles were reversed. I'm not even sure it would have occurred to me. Now I may very well have sent the PC to do some research/mentee program and used those HackMaster tables for the results and hand-waived the nit-picky costs and formal schooling bit, and maybe even tweaked the results as needed, but to skip the tables entirely? Probably not.
Probably just me. I clearly like coming up with, or straight up "borrowing" cool tables and using them in my game. I prefer the creativity of coming up with possible results and letting the dice fall where they may (that tweaking earlier wasn't so much results based, but which tables and modifiers to use).
Now in this case my PC automagically knew those spells, but the GM could have had me roll to see if I actually understood them, based on my INT. Access to said spells is, or could be, one part of the equation. The ability to comprehend could be another. Is there a maximum number of spells of each level my PC is able to learn? Again, these are already HackMaster concepts, but I've seen a mix and match in other systems as well. I could very well see my GM not having these limits because of reasons, but I could also see being presented with a "You already know 8 1st level spells, well that's your limit........" and I don't think I'd even be mad because in-character how the hell would you know there's a hard 8 spells per level limit? Sure maybe knowing there is a limit, but the actual number....meta-gaming right there.
Having played such a strict, crunchy, game for so long (it was strict for the purposes of Tournament play....it didn't have to be otherwise). Not knowing things is really getting back to the OSR roots, more rulings than rules. Of course this particular GM has a tendency to through new OSR supplement ideas at us for playtesting, so even if I knew the original rules front & back I'd still have plenty of new stuff coming my way if we were playing with a more strict direct interpretation of the BX game.
If you're coming to the Tavern from a stricter game, like HackMaster or one of the more current editions of D&D, you might enjoy picking up some dice and playing in an OSR game.