I've done this—I've even added a different rescue address to try to override whatever's in the database—and still get the message, "Your Apple ID cannot be the same as your rescue email address." ... Totally inexplicable.
No. That's the separate "it's impossible to merge accounts" point. (I have four separate Apple IDs for two countries.)
A lot of the bizarro stuff going on here, I think, is because accounts with different histories (e.g., what service they originated with) are still handled differently behind the scenes. It makes no sense, but things really do seem to be path-dependent.
