>>ivraat+(OP)
Because it’s hyperbole. Not in the sense of it not being literally true, but hyperbolic in the sense that it is both an avoidable and limited to first party properties. It’s also not abusing existing standards. Instead of redirecting all browser links through Edge, they made a handler that specifies Edge. Firefox decided that it would ignore this design and hijack links that are specified to use Edge.
Let me give you a real example. Microsoft has a link to manage your Microsoft account online. This opens in Edge and thus can auto-login to your account. That is the expected and secure behavior. Firefox shouldn’t be able to hijack that.
Also you can still use any browser to check the weather. Just not via the integrated windows app.