Don't think they are plants. Wasn't Bo getting boo's even as a face? Or something like that. X-Pac get the fuck away heat was all that I heard. I'm unsure how you can relate his mic work to early Kurt Angle tbh. Kurt always had charisma, where as Bo has none of it. IMO anyway.
I'm pretty sure that they have plants in the crowd, people like Mason Ryan getting pops leads me to only one conclusion. Bo was getting a face pop for a while, they went ape shit when he won the belt and instantly changed when he started becoming more of a heel. And I'll disagree with you there, Bo does have charisma. His promos do have some character behind them, especially since the heel turn, and people seem to react to them so I don't know you can say that he doesn't have charisma.