[ccalloway]

It makes some sense. You don't want to accidentally make some of your edits on one version and some of them on the other version. That would mean that you end up with wrong data, and also have to slowly unwind your changes correctly, if you want to get back the original.

So you have to arbitrarily choose one and keep in your mind that that's the one to be edited. You could choose the 'bottom' one. But because object persistence is pervasive, you choose the 'new' one.