It's a hell of a lot less of a pain in the ass to just say the first decade/century is a year short, due to lacking a proper "year 0", than it is to try and say that all future decades/centuries aren't easily distinguishable by their numerical label.
"The 20s" should be 1920-1929. Because those are the numbers that are "twenties". If you're telling me it's actually from 1921-1930, and that nineteen twenty isn't part of the "twenties" but nineteen thirty is, I'm going to say your position is semantically silly.
It's about whether we need a special rule for one century/decade, or for every century/decade past the first.
Because seriously, saying that 2020 isn't part of the 2020s is . . . bananas.