It would have been helpful if the Poser devs had told us that it had changed, and what to use for the new values. It's actually not clear that they even knew, though. The changed happened because they used a newer version of the Cycles renderer, and they might not have noticed everything that changed.

Given that we do now know that it has changed and to what, it would be helpful if materials recorded their Poser version number and automatically updated roughness numbers when that version changed. Or at least it would be helpful to have a python script in there "update all roughness values for P12" to make those changes for us.

So I think it's fair to say the change was necessary, but also that it could have been handled in a way that was easier for users.