I see it the other way around. I have a feeling that FireFox follows the specs while Chromium kind of has its own plan and directly introduce new behavior without much care for standards.

Since Chromium based browsers have the majority of the market share, you have the feeling that FireFox is awkward/lag behind. Now look back at Opera when they still have their own engine and you will see that while they try to introduce new behaviors just like Chromium, their limited market share means that people don’t feel the need to make use of these “innovations”.