Yes. And no. It depends.

The "right" amount of float is good, more than that amount is bad and can cause injury.

Float needs are specific to each person. If you have stable feet that don't pronate or supinate, float won't matter much.

"Knee pain is caused by too much float as often as it is caused by a lack of float."

Another thing about float: the bigger the float, the more you have to rotate your foot to unclip from the pedal. I tested some 9º float Look Keo cleats, but they required a massive effort to unclip. Now I use 6º float cleats, which I find much easier to clip out.