Almost certainly unintentional. They're likely confused by a new User-Agent string or some feature detection gone wrong.
For example; Google is a technically advanced company, so they must have a CI check somewhere in their Youtube release process which confirms that a suite of browser tests pass before a greenlight is given on release. Do you think Chrome is one of the browsers included in this test? Do you think Firefox, Edge, and Safari are as well? Given all of the external evidence we have that they continually break the experience for non-Chrome users, even if they were just oversights.
Maybe Edge released an update that changed a UA string, Youtube is too strict, and it had nothing to do with a new release. Now ask yourself: Is there any chance something like this could happen with Chrome? Of course not; they coordinate and ensure the experience is Perfect on Chrome. Is that less evil, given Google's overwhelming control over the internet?