PWR staking was added a few months ago. Basically, PWR became a mining token and it is another way new PWR gets minted. Gives people an option to grow without having to be in the LP.

APR looks to be roughly 15%, but hard to tell. Some people with stake could answer better but the HE explorer is useless these days to track mining rewards for stuff, unless I'm missing something.

Empo will be able to add more details to this answer.