...and the problem you describe, David, is solved by using version-control software like Perforce—something I imagine PTC developers would be familiar with because most developers use such software. I think that PTC is imposing a bad version of "Save As" on its users under the wrong assumptions.
As a user, I want the ability to save a file under the name of my choosing, in the location of my choosing, as painlessly and quickly as possible. And that includes saving a file with the same name but elsewhere. I do it all the time and it works great. We use version-control software to ensure that the latest good version of a file is in a stable directory that everyone else can access to check out the file.
No need for such features.