His step-through foot is well on the ground by the time he releases the disc. Look around the 9:45 mark and you can see his foot heavily on the ground prior to releasing the disc. Whether or not people will call him on it has nothing to do whether or not it was legal or even ethical. Just seems like a cheap way to cheat. No disrespect meant to him, he's a fantastic player, but this is a game that relies on ethical play and a heavy degree of "self-refereeing." Just seems wrong...
I tried my best to capture some frame-by-frame pictures of the particular putt you mention at 9:40. Unless I am missing something that you can see, the quality of the video makes it impossible for me to positively determine whether or not the disc is still in his hand when his right foot hits the ground. Here's the link to the imgur album I put together:
http://imgur.com/a/SnZGV
The disc is clearly in his hand for the first two pictures, with his plant foot maintaining a point of contact on his lie and his left foot still in the air. Starting with the third image, it's hard to tell exactly where the disc is and whether it has left his hand. If I had to make a judgment call, I'd say it's still in his hand for the third image. I would
guess that it is leaving his hand in the fourth, which is also the frame where it appears his left foot first makes contact with the ground. However it's hard to conclusively tell about either of those things from the quality of this video as the disc and foot placements aren't clear enough. In the last one the disc is definitely out of his hand and his right foot is definitely on the ground so that's not too helpful but I figured it would be best to start a little before and end a little after the supposed infraction.
After watching this, I would:
1) disagree with your assertion that his foot is well on the ground by the time he releases the disc. It might look like that in real time, especially if you already think Uli is a rules abuser, but I really think this frame by frame analysis is unable to conclusively show that it was either legal or illegal.
2) think that something needs to be done to address it, even if I don't know exactly what that is. If we can't determine the legality of a certain putting style with the aid of technology, there's no way we can expect players (that have a personal/financial interest in the outcome) to be able to accurately call this.
3) applaud Uli for developing such an effective style that clearly bends the rules almost to the point of breaking them. Athletes and teams in nearly all sports do that to gain a competitive advantage, and even though I might be frustrated in a way playing on his card if I think he might be foot faulting every putt, I think part of that would be envy that he does something that I can't/won't try.