There's plenty of mecha anime with different scales of mech. Even gundam does it some of the time. I just think it's specifically battletech influence that humanoid mechs will be any size and non-humanoid mechs also any size, whereas stuff like armored core might have reverse joint armless drone mechs, humanoid standard mechs, freakier designs be oversized, etc.
I've seen people asking if japan does reverse joint leg mechs much and they do, but they're commonly a lighter class.

Anyway the tau stealth mechs are cool. Riptide feels a bit skinny for my taste, and the stormsurge just isn't very cool. A massive weird armless baby. All the custom parts that give it arms look way better.