Yes but if you are using MF and no IS and it is still slower then it tells quite a bit. The battery / power to run the lens wouldn't matter.

Why would FPS and AF even be tied together? The camera apparently has enough power to focus. Do you have to achieve focus before the R5 takes a picture?

I think Canon saw no need to give much consideration to a lens that was released in 1999. Is it slower because of power or Canon crippling the lens so we have to buy a new version? Both actually make sense.