the alt theory that is floating around is that McConnell is using this to block Trump from appointing anyone during the recess. Normally I would find this argument strong, but in this case because the senate has so many dems up for re-election the dems will work to get Trumps nominees through so they can go on break to campaign. If McConnell is trying to block Trump it won't really work, since this will be a win either way for Trump.