I can't think of ANY reason that anyone would need to know the final build number unless they are running a torrent or illegitimate copy and want to make sure they have the final version copy.
I don't think there is anyway that people will know if 10a432 didn't get additional tweaks before going gold master. I'm pretty sure that Apple doesn't include the build number when they ship cause that is for beta testing. I doubt that what you find on torrents today is the exact version that Apple is shipping.
If you want to be absolutely certain, then buy directly from Apple and you'll have SL on the 28th.

Otherwise, you'd have to wait a few days for it to show up on your favorite torrent site and go through all the hassle of re-downloading. In the meantime, you could have the legit version installed for less than $30. Seems like a no brainer to me.