I don't knock the interim promotion process, but if someone is going to, I expect their logic to remain consistent. Ronda's division didn't exist, sure, but neither did fly or straw, and the promotion could have had a tournament or at least one crowning fight first, so if someone's gonna shit on being gifted the belt, I'll point out she was too.
My point here is more like:
Usually a double champs really only establishes themselves at the top of one division, then get a shortcut to gold in another division, and that's just an accolade and don't go on to prove they're actually the top of it. If they have defenses, it's usually in the division they climbed.
Poatan, on the other hand, has been building defenses and establishing himself in the division he got the "shortcut" to, so it wasn't just a cheat. And even if he didn't defend at MW, he did climb to the top of it, so there's no question of his legitimacy there.
All double champs have different size mountains they staked their flags on, but only really Nunes can argue they truly climbed both mountains they flagged