How is that 'false'? Firefox is 'dropping' those frames, not OBS... and it's letting you know that.
Unless you're conflating dropped frames in a browser to be the same as dropped frames in the output of OBS... which you are doing, and is (to put it gently) moronic, seeing as they have NOTHING to do with each other.
It's like complaining/pointing out/posting that a viewer doesn't have enough downstream bandwidth to watch your 2000kb stream. What does that have to do with OBS? (I'll tell you: NOTHING).
Again, so Firefox performs worse when viewing video as compared to Chrome. How is that an OBS issue? Why aren't you telling the Firefox devs? Why are you posting about a problem in a piece of software that is completely unrelated to OBS, in an OBS Forum?
Or to put it YET another way: What do you expect the OBS Devs to do about an issue in Firefox, and only Firefox?