They do no such thing.

The first link explains the protocol.

The second explains WHY one would refer to client and server with regards to Wireguard.

My point ties both together to explain why people would use client and server with regards to the protocol itself, and a common configuration where this would be the necessary for clarification. Ties both of them together, and makes my point from my original comment, which also refers to OP’s comment.

I’m not digging you, just illustrating a correction so you’re not running around misinformed.