This is such an annoying approach for Google to force people to using Chrome... I get that they're not testing stuff on Firefox, so much is obvious. But there are so many times things don't work properly in Firefox (YouTube loading slower, lag in Gmail, Drive having weird UI<>backend synchronization bugs) at a first glance, but as soon as you set the user-agent to Chrome, things just magically work perfectly fine, and all issues disappear.

Someone should really be doing a deep dive into this issue, because it's been going on for a long time, and is clearly anti-competitive. My guess is that they're really good at hiding this/making it look accidental rather than on purpose.