Nope. If they are willing to have sex with both genders thst is bisexual. That's the definition. Not even The All Powerful Larian and All Powerful Bioware can change the definition of bisexual. It's a cope they came up with a lame attempt to please everyone when in reality it doesnt please. Gay characters should be gay, hetero characters should be hetero, an gay characters are bi.
All romances in this game are bi sexual. This is factz. Your spin doesnt change this.
Bio knew they screwed up hence why DA3 (a game I dislike otherwise), npcs actually had legit preferences almost like they were 'real' people.
Bottom line, all romanceable npcs in the game are bi sexual. That isn't diversity.
I don't think this would be true in EA as it is now, because we could reason that every playthrough is a different parallel universe, and the companions are only gay or straight in each one (just coincidentally aligning with the player's sexual orientation).
However, in the full game we now know there will be full respecs, presumably including gender. So a companion could be in a romance with two separate genders during one playthrough. So I think you are correct that they are really all bi or pan.