Hi SO,
Sorry- just saw your post.
Yes, the vendor wet ages it in cryovac for 28 days, and then it goes into their dry aging room until the desired dry age time.
I have had steaks both 28 day dry aged, and 50 day. There isn't a lot of difference between the two, and cost is higher because of shrinkage.
If you ever get the chance to buy some Waygu 28 day dry aged steaks, do yourself a favor and splurge. Problem is, you might not be able to eat any other type of steak again!