i think we may be using wrong words....i think sloppy may be being used as an opposite to the 'perfection' of bands like steely dan where you go see them live and it's almost as if you are listening to the original recording. I am hoping that sloppy is being used to mean gritty, spontaneous(a good word you chose). That is how i am choosing to interpret what some are saying as sloppy, if not then nevermind
then you are doing just that, 'hearing', not 'listening'...way more to it than that...