Registry keys and / or config files both versions use that the installer may overwrite to default, the same that the uninstaller may clean up, stuff like that. I work in IT, I've learned to expect things like that. Not interested in getting a VM environment set up and a new VM spun up just to get some dll's. That seems a bit excessive. And besides, attention is going to be brought to this one way or another as more extension installers are found that don't recognize the store version.
Excellent, thank you!