I don't like this behavior (deceptive assertions). However: The user being actively steered away from an alternative browser, is unlikely to expose the user to

I don't like this behavior (deceptive assertions). However: The user being actively steered away from an alternative browser, is unlikely to expose the user to 3rd party risk. It might expose them to personal data being collected by Microsoft. Whereas, for example, Apple's latest hardware with Secure Boot, lacks both an Apple signing service for UEFI applications, and the Microsoft UEFI public certificate (which near as I can tell all non-Apple x86_64 hardware does have). Linux distros get their shim pre-bootloader signed with the Microsoft UEFI key, that's how they can leverage Secure Boot. But on the latest Apple hardware, no Linux for you unless you disable Secure Boot. I've found no support document how I can add enroll a key, either my own, my distro's, or Microsoft's public UEFI key. I think the Apple case is provably worse, it does expose users to 3rd party malware.