progression standard for skiers?

when could skiers be considered mastered?  when you can lower your glutes to knee height while turning your thighs 45 degrees relative to your feet?

When your performance matches the Athlete's performance of the exercise in the course video.

Keegan said:

When your performance matches the Athlete's performance of the exercise in the course video.

that was incredibly helpful, thank you...

Whether that was meant to be sarcastic or not, that was the most concise answer I could give. Video yourself performing the exercise from the same angle as the demo video, if you look like the athlete in the course video and you are adhering to the form notes listed in the exercise description, then you are good; no need to obsess about exact angles of your hips relative to your knees.

If you are still unsure post a form check video in the Form Checks section.

athleticandrey said:

that was incredibly helpful, thank you...

I'm not sure whether you're being sarcastic or not. In case you are: Keegan is trying to be helpful. 

The best way to tell whether you're ready to move on is to take a video of yourself performing the movement and compare it to the course video. If you're not sure whether or not you're performing the movement well enough, post here and ask for a form check. 

For skiers, the standards you wrote sound about right, but I'd still take a video to be sure.