Shouldn't there be a separate 'PC' + 'Controller' category for this 'Speed Run' event?

!

Nah.

I remain unconvinced that there is an appreciable advantage practically speaking between mouse, wasd, or controller for the purpose of speedrunning, though if there is I think it simply becomes an interesting dimmension to the planning and execution.

IMO the only reason I can think of would be navigating the various UI screens. M&K is objectively faster in that regard.