"but I see that as a flaw in Lacerte."

You now understand why you do not get a Read Only notice that there is going to be a "conflicted copy" and it's the same type of reason you don't use Carbonite, Mozy, One Drive or DropBox for these file types, either. You can store Backups there, but not Work From there.

This is not Customer Support nor Programming Support. You are on a peer user forum. I hope that helps.