I mean, often, yep. The real reason why they are unhappy with you having an unsupported browser is simply that it's much harder to reason about or enforce policies across bespoke environments. And in an enterprise of a sufficient scale, the probability that one of your employees is making a mistake today is basically 1. Someone is installing an infostealer browser extension, someone is typing in their password on a phishing site, etc. So, you really want to keep browsers on a tight leash and have robust monitoring and reporting around that.

Yeah, it sucks. But you're getting paid, among other things, to put up with some amount of corporate suckiness.