I understand what's your point here.
This is a parser/builder, meaning that you'll have to ask it to do what you want - it won't do anything by itself.
That's why I asked here, to have some insights about this specific type of external asset - obviously I'm not going to use it until we got any official confirmation that this is allowed.
This part of the rule is what is making me thinking this could be allowed:
Asset store assets are not allowed either, except for the ones that don't contribute to the game itself but make the workflow easier.
Even if this lib isn't from the Unity Asset Store, it is still making the workflow easier and does not contribute directly to the gameplay, visuals or whatever the game is offering.
Thanks for your react on this!