Thanks for the response guys. About the last point, are you saying the PF and C don't need jumpshot at all? That doesn't sound right..
I think jumpshot is crucial for the powerforward in Look Inside (and probably helpful for the centre). If you actually look at a game where a team plays look inside you'll notice the powerforward taking a lot of short and mid-range jumpers. (I suspect that it happens when he can't beat his man off the dribble to get closer inside, but that is an unsubstantiated guess) It's somewhat unclear as to whether or not inside shot matters at all for short range jump shots, but it's likely that jumpshot plays a central role in determining if the shot goes in (it may be the main or even only attribute that matters on those shots).
So yes, JS matters for PF in a look inside and low post offense. Particularly at lower levels I don't think you need super high jumpshot because opposing players will have low OD, but I think you need decent jumpshot on a PF to run inside offenses.