Enough happens between 18 and 22, that one can probably guess a difference, but not for 19 and 21. And even an 18 year old can appear 20s and a 22 year old can appear like a minor, so its all one big thing under umbrella of ‘brain not fully developed but we let them drive, have sex with whoever, and kill people’.
And when you’re getting older and older, ‘kid’ moves from 14, to 16, to 18… but also to 20, 22, and eventually all of 20s, with 30s becoming ‘still young’. If you’re a legal adult that looks like you might not be, like it or not, but large swaths will still regard you as at least kind of a kid. Different political types will decide what to do with that, from ‘you’re just a kid, nothing you say matters’ to ‘you’re the young (adults) that will be the future so maybe your activism really matters’.
Yes I temper everything going on with my early 30s self with ‘the future is yes, but worse!’. Though I do seriously intend on turning some of my fitness around this decade, so I might at least be fitter and more comfortable than my late 20s, illness/etc permitting. Generally, 30s is when the olds starts being a legitimate topic… but only that, and 40s is when you start-to-get old but arguably aren’t…reallyyy.