G, not many folks have undertaken the sort of new release evaluation of MSB at every vintage at varying release dates such as you.
Given the whole process, every stainless steel tank could be different by degree, some more different than others.
May be the 2012 harvest was erratic ? Rather than the wine production ! Different picking dates, different pressing dates, slightly different fermentation temperatures. The chemists can't cant get it perfectly similar every tme.
I don't think it is yet possible to make a wine, quite in the same way as Heinz make their Baked Beans (afterall, the actual taste of the harricot bean is a very minor part of the flavour
). I dunno - May be it is ?
I hope you are not too "put-out of sorts" by this variance this year. I'm damn near hopeless in judging a new release white wine, they change so quickly after opening. Spritz all over the place with some, I think you've chosen the hardest path to follow, when looking for particular attributes and nuances.
Good luck with them, don't give up.