Yes its a possibility I guess as my nikes are different to my ccm's, as you mention nike seem to be a size bigger than what they should be, however KOHO is CCM which in turn is now RBK for the 6100 series, so I would of thought they'd kept the jerseys specs the exact same size just swap out the makers logos on the back that's all.
That being said again I'm starting to think my nike Leafs jerseys from 1998-99 are longer than my Canada 2002's, and my Canada 2002's are shorter than in length by a few inches to my rbk 6100's, stupid because a 56 should be a 56 a 58 a 58 etc regardless of maker should be standardised sizing