My understanding is that the judges are told to judge what the riders do on the wave. The presence or absence of straps is irrelevant.
It is implicit that they are talking about surfing moves on the wave face.
The point of view of strapless riders is that it allows you more freedom of movement to better surf the wave. If you're expecting to get extra points for riding strapless because it is harder to do then it is clearly not a better way to surf and you are a guy. They should use their superior skill and their chosen method of surfing to surf better and get more points.
Similarly, a strapped rider cannot throw in a big boosted air and get points for it because the rider is not surfing the wave, they're dangling under the kite.
My personal opinion is that a top rider, riding quality surf, without straps is a thing of beauty.
A lower level rider, riding without straps because the cool guys do it, is a guy.
Furthermore, I think there should be a licence for people to ride surfboards with kites. I am a bit tired of dodging out of control gumbies who have no idea trying to ride their surfboards when they can't gybe, can't ride toeside and probably can't even ride a twintip properly.