Probably. A surprising number (or perhaps just a surprisingly vocal number) of people here consider any lesbian content in a male protagonist game to be NTR.
First off, I don't consider anything in this game to be NTR. There's no romance tag, there's no harem tag, and the relationships can be player-defined, so there are no "canon" monogamous relationships to get jealous about. Second, I agree that lesbian content by itself isn't cheating or NTR, and it's a ridiculous opinion to hold.
That said, I see the polar-opposite opinion to the one you mentioned to be more common (see Tokenug's post just above mine), which is equally confusing to me. Many players think lesbian cheating doesn't count because another dick wasn't involved. IMO, cheating is cheating regardless of the equipment used during the act.