On the other hand that's a standard negotiating ploy.

How many times, when buying a car, are you minutes from closing the deal when suddenly a new fee appears. Or suddenly an issue with your trade-in and it's not worth what they "thought" it was. It only changes your monthly payment by $10... do you really want to walk away after the effort you've put in to this point?

So not necessarily anything nefarious going on (though not discounting the possibility entirely).