Instead of calling Chögyal Namkhai Norbu Rinpoche's Longsal Teachings "termas" or "mnal chos", how about:
Now I don't think that Chögyal Namkhai Norbu refers to them as such, however I also don't think that rMi-lam gTer is a terminology invented by Jim Valby, John Myrdhin Reynolds, or Rangjung Yeshe Wiki either.
Well, I guess they didn't invent the term, but since you mentioned it -- if I google for "rmi lam gter", I only find websites/dictionaries referencing to either Jim or John. In comparsion: if I google for "sa gter" (earth termas) for example, I find quite a lot of different references beside John & Jim....
Anyway, all I know is that ChNN's "klong chen 'od gsal mkha' 'gro'i snying thig" is also called Longsal Terma Cycle
, and the different practices/teachings from the Longsal cycle are called termas as well (for example, "Oral Commentary on the Longsal Terma The Opening of the Gate to the State of Ati", etc.). And since milam termas are apparently only one category of termas, I see no problem in calling these teachings from ChNN just termas.
What I'm wondering about is that statement from Mutsuk, i.e., that the Longsal cycle is styled as "mnal chos", which is, according to her, different from a milam terma (and also different from termas in general)