For the past couple of months he's been exclusively on chess.com, with the exception of exactly 1 15 second game he played on Lichess, so I think his position might also be a bit more nuanced!

Lichess is great if enjoy the flagging meta, and not so great if you don't. It's made even more extreme by their interpretation of sufficient mating material. A single knight is generally counted as sufficient mating material so you end up scenarios where you're forced to play N v N along with 0 second premoves and that's not something I much enjoy.

I understand some folks like this sort of stuff, which is why it's great that there are multiple sites competing instead of a single site monopoly.

Probably and I was nowhere near that level, I just played for my county and tried for my country as a kid, but it changes blitz massively and should be it’s own game. It’s not a thing you can do IRL, so unsure why it should be a thing in the online representation of that.