Why is Pavlo vs Aspinall an interim fight? Jones being stripped of his belt would appear Sergei Pavlovich vs Tom Aspinall fight for the vacant belt.
The whole idea of an interim belt is for situations like this one when the champion is unable to fight for a long period of time. Jones wasn't quite stripped off of his belt, it's more of putting his title on hold. When he is back, he'll have to face the interim champion for the undisputed title.
The news says it will take more than a year before Jones can recover, it's very uncertain whether he can still fight as long as USADA has yet not out of the picture he will not be able to. Its the same issue with Conor.
Jones's career is full of unfortunate events. He got to the very top effortlessly and (if I'm not mistaken) he was the youngest champion in the UFC's history. If everything went right, he would've had even more impressive record. But he still has the most title fights in the organisation.
Other than the recovery period issue, there's also a question if Jones will be willing to fight whoever holds the interim belt. He seemed quite picky in choosing his opponents recently.