I can confirm this- I had a new player lose their mind when they realized I wasn't using the optional xp awards. They had showed up to my game with an Elven Ftr/Thf/MU and after the first session, I expressed my doubts about their survivability going forward. Even with my approach to multi-class hit points (when told to halve or divide hit points by three, I would track fractions of hit points to prevent unfair "salami slicing"), just the idea of needing 3750 xp just to get their 2nd Thief level and a third of a d6+1 hit points (15 Con) was worrying to me.I don't know if I'd characterize it that way. I mean, yes, the various guidelines for non-combat XP awards were easy to overlook, and often relied on DM judgment calls (which I suspect led to arguments about whether or not a DM was assigning XP correctly), but I suspect that if applied liberally they had a fairly decent overall chance of replacing the XP-for-GP standard fairly well (though that's based purely on my eyeballing it).
"Yeah, but I'll get xp awards for each of my classes, right?"
I blinked at him. "Say what now?"
I'd seen the optional rules in the DMG, but as far as I knew, none of the other DM's I played 2e with were using them, so I hadn't bothered to add them. So when I explain that, the guy was like "I can't play in your game, that's entirely unfair."
I was completely at a loss- if I was supposed to be doing this, why was it presented as an optional system? And tracking each action a character made, like tracking video game achievements today, felt artificial and strange to me. Of course, I soon realized that to achieve higher levels by slaying monsters along wasn't going to work- I used a lot of modules back in the day, and if a module said "for characters of 4th-7th levels" and the next one I had was "for characters of 5th-9th levels", I knew people were going to have to go up a level and a half or so during the first one, so I stopped using monster xp entirely, and just gave out large chunks of xp over the course of the adventure- I guess it was an early version of milestone leveling, thinking back on it.
No one seemed to have any problem with this approach, at least.