WebRTC isn’t really a big concern. The maintainer of the Arkenfox project who has also worked with the Tor Browser, has stated the following regarding WebRTC on Mullvad Browser:
“You do not need to disable webRTC, as it is already protected by mDNS and is gated behind user gestures - the user must also explicitly opt in per site, per session to start sharing. WebRTC support is trivial to fingerprint.”
I think it is, I have noticed that the higher up the service is the more of the criteria it checks, but sometimes this is not true, and it goes into another criterion.
What questionable business practices has Proton engaged in?
The answer you linked confirms that there is order for some tool categories, whilst others are not so certain. Even for the others categories, of which not all are authored by Jonah (hence, the uncertainty), I see a clear order and non-randomness. I assume this is because the tools can be assessed directly for example for their features and price, and products aren’t identical, thus, ranking them is very feasible.