Never heard of that site nor can I test it, I'll just take your word since I can't find any examples myself. Clearly a bit toxic against Firefox here lol.

Web market share doesn't mean anything. Web follows standards decided by w3c that every web renderer follows. None of them get it exactly right because web browsers are extremely complicated and there's all sorts of edge cases. When Chrome or Firefox have mismatching behavior, the one following w3c is correct, the other one is objectively bugged. This is not opinion, this is following documented and mutually-agreed standards. Which Google and Mozilla are both on the w3c commitiee. I'll let you look into if you care. This also doesn't mean that Chrome will fix all their bugs either.

Just going to disagree with you with the UX because it's clearly subjective, but modern UX design heavily disagrees with you. Having a single visible button for every possible action is not good. It's a waste of space and clutter if it can be condensed or moved to a more intuitive action/gesture. More screen space the better.