This is the benign explanation I was looking for. It's a clever hack for providing a good user experience for the person who's receiving remote support, who can't be assumed to be computer-savvy.

Of course, it would be better still if there was a standard way of setting up specific URL patterns under specific domains to automatically launch an associated desktop app if that app is installed. iOS can already do this through the "/.well-known/apple-app-site-association" URL on the domain. It's why Zoom and Teams links, when opened on an iOS device, always go straight into the native app once that app is installed.

Edit to add: BTW, the file at the well-known Apple path also gives me a way of detecting a Zoom invite URL in one of my own products, even though Zoom URLs can have custom domains.