Pair chess is actually pretty common, especially among people who aren't experienced chess players.

There’s “pair tennis” (I know nothing about tennis, so apologies if that’s not what it’s called) which seems to flow alright, but tennis is a much more tightly constrained activity than programming. There are only a few actions each player appears to perform, with all other actions explicitly falling out of bounds set by rules of the game.

Chess is a much wider problem domain. I can’t imagine anyone playing pair chess.

Really? You've never seen two people on a team playing chess (discussing the best move, etc)?

Each player has his own board side so you wouldn't notice.

https://en.wikipedia.org/wiki/Bughouse_chess

I assume that's what he meant.