This is not just for you gymnasts working on your planches, but also for Olympic weightlifters.
Since in Olympic lifting you are spending a lot of time with your wrists in extension, it might be wise to get in some prehab work done by focusing on flexion.
Of course once you get more comfortable with this you progress to something like wrist push ups (maybe first against a wall, then on the floor etc.)
Check out more drills on Mobility 101.
In the second video he is doing something similar to what Kelly Starret has taught us along the way. First distracting the joint, then stretching.