"Sealed" as in "no disassemble, no service, no rebuild".
I did not do the water dip, and my cars also run noticeably faster after break-in. In fact, it wasn't until after the first break-in pack/cool down/tweak/run again that I noticed how weak the stock diff is. Once broken in, the motor overpowers the diff pretty easily.
I think we all agree that a break in for the motor is needed, what we don't all agree on is the "How"
I just don't think doing a water dip on the stock motor (especially if it's the only one you've got) is a good idea. If it was rebuildable, maybe I'd try it. I just don't like the idea of not being able to examine the comm and brushes after doing a water dip, and getting the bushings completely dry and then re-oiled.
I think for a noob the dry break in is the easiest, and least likely to cause a fatal mistake to the motor.
I also think that either method will work, and that one or the other should be done to get the most life out of the motor.
But what's most important here is that this is my opinion, I'm no expert, just an old fart
(oop, can we say that in here?)