I'm not sure, never looked into them properly. Maybe can give us some insight on that.
I'm assuming there's limits and it's not offering just self-votes back but also something that highlights your posts on their dapp as it goes through it. I also doubt the focus there is to maximize rewards for posts and returns for delegators where that's the main shtick here with hive.curation.
As you said yourself the 16% APR is too good to ignore, yet you ignore the effects it may have on the ecosystem or your investment in general compared to proper curation and distribution of inflation.
RE: the @hive.curation scheme