I've always wondered about that. I fish the spillway, but throw them back. I see a lot of people keeping fish there. I would think that the crappie come up the creek to feed on the stuff coming out of joe pool as opposed to the fish in that area being different from the ones in Mountain Creek Lake. I don't know what the real answer is to this. Mountain creek is now on consumption ban as opposed to possession ban, so the levels are coming down but still, to be on a possession ban they had to really high.
Yah I am not sure either. Probably a mix from both water bodies. You probably won't grow an extra arm and leg eating the fish from there, but I'd rather play it safe and just fish elsewhere.
To the OP, yes there are decent crappie in MC (and also up to the JoPo spillway at times).