a little straightening is ok, the most important things about the right leg is that the angle remains the same and that tension builds up, not the knee flex
now if he straightens up this much on an iron then it may be too much on a driver, but if it stays about the same IMO no big deal.

Tony, when you gonna post a face on because from behind looks like there are not many big issues, but face on could give us a whole new perspective, or reinforce the idea that there is not much to clean up