Weirdly enough I find that Firefox works better than Chrome with Hangouts a lot of the time
This is also why Macs get scorchingly hot when using Hangouts on Chrome.
But yes, it's generally Google forcing their own products, just like what they're doing with YouTube, where you also get VP9 on Chrome and H.264 on Firefox.
Firefox is getting H.264 only because it doesn't support MSE for VP9.