They're not mixing it up, they're rewarding and trying to move forward to the fighters they want having belts or getting what they want, they know it's not going to work for all the cases but their view on it, is they are going to try to load the "star gun" with as many bullets as possible, rankings and sport be damned because they have no idea how to harness the actual sport into an attraction and have given up.
Since Miesha has the belt, they think Ronda will get a better chance at taking it back and want to take it back faster this way.
If this had been Holly vs Ronda 2 and ended that way, the third fight is immediate. They're only rewarding their favorites in direct or indirect ways.
Under the logic they gave Conor now, they would have given GSP the Serra rematch immediately, both stoppages, both huge stars in at least a country and location to use, but they didn't they did TUF with Hughes and GSP fought a Contender. They used to try to both legitimate rankings and aiming for peak events, but since Ronda they have just stopped entirely caring about any rankings legitimacy when there's a star in that division.