I don't even see 2013 6er models in this list. Besides, I would tend to believe the BMW website and press releases over some website that tries to collect data on every vehicle on the planet. Especially when the two former sources agree.
That said, I cannot be 100% certain unless I open the diff and count the ring and pinion gear teeth myself. 640s may have different ratios than 650s, but I think we were just discussing 2012 650 vs 2013 650.