SEP 12.1.5 build number

OK, it's not a great thing, I'm just curious. I stumbled across the build number of SEP 12.1 RU5: 12.1.5337.5000.

In the past, the numbers after the main version pointed at RU and MP (e.g., 12.1.1101.401 was SEP 12.1. RU1 MP1, SEP 11.0.7300.1294 was SEP 11.0 RU7 MP3).

Is there a change in the build number creating policy? Or (hard to believe) did Symantec swap the third and the fourth number family?