You can tell if a stock 2012 has the fat50's because they also have mismatched aged white pickup covers and knobs... the non fat 50's ones had knobs and covers that matched the pickguard. Of course that stuff is easily swapped out, but it's a good rule of thumb if you're looking at used 2012's.
As mentioned some older 2012s still have the regular American Standard pups which are very good. The fat 50s are very good too, just a little different with less winds I believe, so won't be as powerfully voiced. Either pup will provide the expected Stratocaster tones.