IF I remember correctly, they contacted me a year or two back. Basically they say they will use their positioning on Getty to sell your images - but you sign your images over to them to put onto Getty as their work so they can sell. Whatever they sell of your images, they pay you up to 40% of the commission. For example. Your image in their portfolio sells on Getty for $500, and they get, for example, 50% commission so $250. They will pay you 40% of $250 i.e. $100. You get $100, they get $150.
I declined politely.
If I want my images on Getty, I will sell them there.
They are basically offering their position as an agent on Getty and for it they get paid more than you do.
Caveat - this is all IF I remember correctly.
ETA - I'm pretty sure with me they were talking about Alamy though.