you mean kinda like how you have to upload a photo of your face to do the same in Britain?

we use language in different contexts. In the food store “fruit” has one meaning, while in a botany paper, it has another.

This doesn’t say theres no such thing as fish generally, it says there is no useful definition for it in a biological setting.

2000s: Actually, fish aren’t fish

https://www.sciencealert.com/actually-there-is-no-such-thing-as-a-fish-say-cladists