Reset protection does require new hardware to my understanding. It requires a specific new set of SOCs that has the feature available in the UEFI BIOS. Not sure if the SOC for the L635 has that or not, but Reset Protection is not available on mine.
As far as some (or many) not yet seeing the update, I'm beginning to wonder if AT&T was sending out to a small sample as a test market before final roll-out. Microsoft is showing it available for AT&T for distribution, which means AT&T must have agreed to distribute OTA. We have at least one user receiving it here on the forums, and I've found someone (a family member) who lives about an hour from me that has also been notified of the update, but has not yet installed it. She wants to wait until I'm over there for a visit this coming weekend in case there is a problem with the update, so I'll find out more about this "update" she has waiting then. She's got the AT&T L635.
Usually carriers do a gradual roll-out to keep from overloading their servers. They don't want to send it all out at once, so it gets staggered to different regions a little at a time, and sometimes can take a while.
That's my understanding of all this at least. Take it all with a grain of salt. If you're not getting it and really, really want it, there are ways to get it.