I think Alamy does allow fully RM files to be available elsewhere, I don't know if they ask you to notify them of sales but I think it is a bad system. What if you have an RM file that acquires topical interest and two agencies start negotiating simultaneously for exclusive usage rights? As these agencies take ages to tell you what they are doing, they could both conclude conflicting deals before you know anything about it - and that could cause big trouble.
That's why it is my opinion - and nothing more than that - that RM files with possible exclusivity guarantees should only be at one agency.
I don't have any fully RM files there any longer, they transferred them all to L years ago (while deleting any that had sold on the RM license)