Your ending makes sense. This minnowbooster is essentially just doing "curating". It's paying you for your power.

Nobody goes into business to lose money. So, this minnowbooster must be shaving a percentage off, somehow -- the question is how.

I suppose an argument could be made that it is more "automatic" than your own curation, so getting fewer rewards for lending your power might actually make sense, so you can go fishing or other leisure activity. :)