I'd say it even makes a difference for single player games that don't "phone home" - I was actually thinking about this the other day in relation to the recent

I'd say it even makes a difference for single player games that don't "phone home" - I was actually thinking about this the other day in relation to the recent (and mostly welcome) trend of remastering older games, and how these releases seem to vary so widely in quality. Obviously I don't know for sure, and there will be other factors like money / time spent on remastering, but I'd still wager that e.g. the fact that the Metroid Prime remaster was able to add in a (seemingly) whole new lighting system and control scheme whereas the the GTA trilogy remaster couldn't even get half of its weather effects working probably speaks volumes to the respective code quality of their originals. Either way, I'm certain that I'd much rather work on porting / patching / remastering a game from a studio that's following the advice Carmack gives here.