Yeah, it's weird. Like, having Page vs Mox to decide who'll face Tana at Forbidden Door wouldn't be the worst idea, since it's the former champ and the #1 contender. Those are the two top dogs in your division, makes sense one of them would hold the interim title.
Having a Battle Royale to decide who's going to face Tana would be okay, too. But when you already have the #1 guy defined, why not just go with him vs Tana for the Interim Belt to begin with? It feels like adding extra steps.