Lanefan
Victoria Rules
If he'd read the 1e DMG he would be speaking only of DMs: as the DMG was off-limits to players, it only follows that players would tend to be unaware of its contents.I don’t think he was speaking specifically of DMs, and I certainly expect there were plenty of players who weren’t aware of it, especially since a lot of DMs didn’t use it.
Yes, and this is a valid point.Maybe poor choice of phrasing here, but the broader point is to contrast a play style that was very focused on dungeon exploration to one that’s more focused on serialized storytelling.
That hasn't changed, though, at least IME. Players still play in more than one game at a time, and overlap between games - it's kind of a six-degrees-of-separation thing.That doesn’t contradict what he said though. Is it not true both that groups often had consistent cores and that players wouldn’t always play with the same group?

There were games played this way, yes. But I think they were in the minority after 1e was released.I think he assumed this because, as he says in the video, he has experience with West Marches play, where this is often the case, and he has conflated that experience with old-school play because of other ways they are similar. At any rate, it’s not untrue that there were games played this way.
It happened, yes, but again not to the near-universal extent posited. Then again, on typing the below it occurs to me we have swapped over a fair number of characters in our crew - it's just so minor a thing that I don't even give it any thought. So maybe I have to concede this one to the video guy.It certainly overstates the degree to which this was a thing. But is it not true that people would (sometimes) bring the same character to different DMs tables, and that things like XP and items would (sometimes) carry over between different tables?
Myself and another DM have pretty much always gone with Gygax's idea of connected worlds, and over the years there's been a fair bit of bouncing back and forth between our campaigns. As of right now, there's one PC from a world of mine active in his game and one PC from his active in mine. 20-odd years ago, a party from my campaign jumped to his world, he DMed them for an adventure, then back they came.
I've taken in maybe two characters previously played in anyone else's campaigns; one because its original campaign only lasted about three sessions and another because it was a favourite of its player (and yet, to the player's credit, not stupidly overpowered or wealthy), Oddly enough, the second one (in-character) ended up going back to its original campaign/setting after a few adventures in mine.
I've had three big campaigns/worlds over the years, and characters have bounced between them now and then (usually an old favourite being brought forward), but I see that as a bit different in that those characters have never had a different DM. I've also had a few characters bounce out of my campaigns into others and not come back, and in one case an entire party (I was overthrown as DM; the incoming DM took the existing party and moved it to his setting, and I became a player).
Overall data, no. For my own games, I could whip up the numbers pretty fast if you like.Certainly this was far from universal, but give the guy a break. He’s just recently learned that this was ever a thing at all and excited to talk about it. Can we not forgive him for making the mistake of thinking it was more common than it was? Do we even have data on how common or uncommon it was?