Which makes it not chess; i.e. not fit for purpose. And this omission is more on the scale of missing castling than en passant. Some people who futz with two or so moves will think it's "fine" but it's missing something critical.
Funny that you mention castling. Most of chess rules were consolidated back in 1500s with barely nothing needing change since. Still, every now and then some absurdity ensues leading to rules change, like the time when FIDE was forced to review the wordings on castle:
Question: Did people not use to play chess before 1972? If every tiny incompatibility with the specs make the game different, then surely people before 1972 were playing a different game? And that's just chess, pretty much every major games see changes in their ruleset practically every year.
You are obviously going to say chess is whatever the rule is in _current year_, sidestepping that philosophical examination. I don't want to get into that either when the bigger problem is in the claim that any deviation makes it "not fit for purpose". If the purpose of a game is to conform perfectly to a spec defined by someone else, then everyone playing football for fun with makeshift goal posts everyday in the field near my house mustn't have gotten the memo.
Exactly how jaded must programmers be from having to follow client's specification all the time to have this outlook?
I would think the neighborhood kids playing football know they aren't playing on a regulation field. If you change the wordle rules and tell somebody it's wordle, do they know the rules have changed?
The kids go back and tell everyone they had been playing football, indeed knowing they weren't playing on a regulation field. And no one in the world has a problem with them calling it football, again despite knowing they weren't playing on a regulation field.
