I think one of the important things to separate out are "narrative mechanics" vs. "critical and fumble mechanics". Because I think a lot of DMs-only (as opposed to GMing other games) conflate the two.
And with that distinction, no I don't feel that D&D has unofficial narrative mechanics in the 1 and 20 at the tables I play at or "in general". But since they are unofficial, in other words homebrew, some tables may definitely play that way. And I can see this, like many other house rules, infecting groups that have player crossover such that it seems ubiquitous among the various groups someone has access to.