...for a secondary insurance that doesn't have to pay full benefits because the primary insurance covers what it covers. I also think it's dumb that you can't pick which insurance you want to be primary versus secondary. If you only had 1 insurance, they'd pay what they pay. So pay it! They don't set the rates based on if they are primary or not - so they should just expect they'll have to pay as if they're primary every time and let the insured decide which is which for each medical event.
Granted - that's my off-the-cuff response knowing very little about why they do things they way they do and assuming it's because they are greedy money-grubbers looking for ways to pay the least amount possible.