The reason it's like this is because the only way to reliably grab it is to cut the string at the first hyphen - then the rest can be almost free text.
It you do it the other way it's harder. You can try this with nix commands /nix/store/<hash>-x is a valid way to refer to something in the store most of the time.
You could just use the last hyphen. It's not as simple since you need to scan the whole string, but it certainly doesn't seem like a challenge to me.
Yes but why pay that runtime cost for a problem the user can solve in human time using grep?