Just speculation but perhaps the way the installers work makes it appear to Windows that the app was uninstalled first and then a new version is installed. If it looks like it was uninstalled then I can see why Windows might change the default.
Which feels quite amateurish and thus ridiculous for Microsoft. Like, they invent a new app store in Windows 10 and they still can't even be bothered to implement a working update routine that isn't infuriating to end users?
