The distinction just isn't important to me. If I see a big talking lion sounding kind of like Jesus and bitch-slapping witches, I'm gonna say "Yeah, that's Aslan, and it's from C. S. Lewis's Narnia books," rights be damned, whether or not this particular story mimics one of the books specifically or not.

As I recall, the rights issue has come up previously, with Tolkein's blue wizards. Maybe it was Bakshi's Lord of the Rings animated feature. For whatever lawyerly reason, the rights had been granularly granted to the point where they could talk about the wizards, but had neglected to secure the right to say the names of these incredibly trivial characters who aren't even featured. So Gandalf refers to them, but has to say some nonsense about not remembering their names. Silliness.

I'm sure this is more of same. They have the rights to this, but not that, maybe they can say the name of one tree because it was mentioned in a poem in Two Towers, but not this other tree because it was only named in Silmarillion.

I don't know about you, but it doesn't matter to me. They're clearly pulling a bunch of stuff that may have been mentioned as an aside in the Rings books, but much of it was further fleshed out (maybe by J.R.R., but more likely by Christopher and Guy Gavriel Kay) in Silmarillion. Whatever it is, it's not completely original content.