My tests from 2 years ago showed the same thing, both /24s were behind
the same system in Exodus' NYC DC in Manhattan (IIRC). That is what
prompted me to move everything to the rcom partner side which uses eNom.
I don't know about a "partner" side but their premium service was always
run by Register.com themselves. The servers were in a number of locations
across the world. Whether any of this remains true today I have no idea.
Register.com may have also resold eNom services but I doubt that had
anything to do with their premium service.
-Don