I think Interim titles, in general, are crap.
It's especially so for this instance. Conor isn't not defending his title due to injury, he's just plain refusing to defend his title. As with boxing if you refuse to defend it you're stripped of it.
Conor (and Dana) is looking at the payday over defending his title, and that's 100% completely fine if that's what he wants to do, but in choosing the payday he should be stripped of the title. Not to mention that he's going to have one hell of a time getting back to 145 after this fight, as odds are he'll work to put decent weight on so he's not at a disadvantage.