i'd have to agree with most everyone else in here, i don't like it.. imo, just keep the loading vertical (traditional oly's & their variations), then just tie in "horizontal movements" using med ball/weight throws+tosses/double and/or single leg bounds for distance, sled work etc.
what i don't get is how that has anything to do with mountain biking?
Maybe he could do a regular snatch but then that does require a bit more balance and ROM, and in fairness, he has no need what so ever to hold a weight overhead.
Stupid? No. Unconventional? Yes.
in that same respect though, he has no need whatsoever to throw a weight forward such as he's doing.. The only thing he should worry about is improving hip extension/knee extension/knee flexion strength/power, general upper body/core strength, and training specific via mountain biking + mountain doing bike exercises in very difficult gears etc, imo.. Is he going to improve hip/knee extension/knee flexion more using that variation, or traditional variations such as snatch, clean/snatch PULLS, high pulls, squat etc? One major problem with that exercise would be how long it takes him to "reload", with traditional oly's and their variations, you can keep the intensity low/moderate & then target the energy systems more specifically towards mountain biking.. ie cluster sets of 10 reps on snatch high pull, etc..
so ya im confused at how that at all ties itself in with mountain biking.
peace jack