I think you are asserting that as a premium passenger, no matter what kind of fare you booked, you get priority during IRROPS. I'm not sure that is correct. You may have priority due to a higher fare class, but you can have a low fare class with a premium booking anyway. And elites get treated better in general , with special phone lines and etc, that even passengers in premium without status don't get.

And in terms of IRROPS I feel that it all depends on your interaction with the agent. If you have everything planned out, alternatives flights researched and ready to be spoon-fed, then you may get your choice over someone who has higher status/premium fare. Also, it may be limiting on your premium fare as you have less options for IRROPS because you want to stay in premium classes.