I recently was assisting a customer with their Power BI licensing and what I found is that in some instances they were having licenses for Power BI Pro and Power BI Premium Per User.
By going through their licenses and assigning the correct license I was able to save the customer approximately 20% on their Power BI licensing costs per month. And over a year this adds up to quite a bit!
This does look to be more confusing than it really ought to be. I’m not sure of any reason why you would want to have Pro + Premium at the same time, so that state should be unrepresentable.