Cool. This issue has been visited before, in case anyone cares.
2016, 2018, 2019 and now… 2020.
I wasn’t going to mention it, but @timetocode said…
It seems… it’s the future. 
Oh yeah, hi xav, welcome aboard, and sorry if no solutions have been found, yet.
Firefox/Mozilla MIGHT be “holding a hard line” on this… because of what they say in the 3rd paragraph… here.
“hardware-agnostic”. A pointer… can be generated/directed by ANY/MANY devices.
Conversely, a mouse… is a specific hardware device.
They’re correct, I suspect. An interesting situation.