(I work on the Javascript engine in Firefox, and improving our story here is one of my personal top priorities, as well as an organizational priority).
The whole point of standards push over the years was so that developers could just code to the standard and the browsers would either catch up or suffer the consequences. It seems like these days Google is dipping into Microsoft's old playbook for every trick it can find to get people to switch to Chrome.
You are meant to zoom in on a locality on the interactive map, and then pan around by dragging. Panning works fine in Chrome. The panning is so slow in Firefox Mobile it's unusable . (It's fine on Firefox desktop, but I'm guessing the shear horsepower available on a desktop CPU hides the problem).
It's a bit sad, because it's a page I use a lot. Whatever it is, it effects a lot of similar pages.
I'd love to know the technical reasons behind that.
I haven't verified it myself and I couldn't find a reference with a quick search, so while it sounds plausible, it would be great to havd a credible source to refer to.
Probably some in-house framework they use that happens to use this old browser API. And they haven't gotten around to fixing it.
Of course it's also reasonable that nobody is pushing a fix up because it works fine on Chrome and that's what Google wants us to use.