You are right about the registration part that has changed. What was confusing with the registration process was the flight recommendations that required agreement as part of the registration process. Some of those recommendations are not applicable or enforceable per PL 112-95 sec. 336. As well as the need to register in the first place, as it turns out.
There is question whether the FAA regards an infraction of 336 to mean you are now automatically a part 107 pilot. I've seen argument to support that as well as evidence to the contrary.
The part of "stay below 400'.......realm of hobbyist" does not apply to hobbyists. Just to clarify. The LOS does apply, just not the height restriction.
I think you're mistaken. The way that the FAA knows you're a hobbyist is that you fly under the hobbyist community guidelines. And if you don't have alternatives to the AMA, then you're stuck with 400'.
If you violate the community guidelines... then the FAA knows you are not a hobbyist. See how that works?
Now you're a UAV, non hobbyist.