Indeed. They "sell" the loan and get a spiff of some sort. Every kid on the corner knows that. It's in their interest for you to keep the loan and hence their interest in you doing so. But, as I said, they have nothing to do with the nuts and bolts of the loan.
Guy I spoke said there is a minimum loan amount and a minimum number of payments to retain the rebate - if paid off early the rebate is charged back to the balance. Presumably this would all be detailed in the paperwork. This came from a salesman so probably questionable info at best.