Anyone look at the efficiencies of the later batches?

I was talking to my buddy who has a bunch of Batch 6, 4.05TH ones running at 4.4-4.5TH but only using 1150-1190Watts at the wall with EVGA 1300G2's.
He told me a few were even clocked at 4.2TH when he received it from factory at 625MH.

So that works out to be more efficient than all the other batches, no? I'm talking about real world @ wall usage , not the BS they usually advertise.
Maybe Batch 6's are the ones to get and Batch 7-8 is to be avoided like the plague as a LOT of them are having issues.