Perhaps. Is there a possibility that potential buyers would be turned off if they see GD charges a 25% commission in general.
Certainly, technically doesn't matter to them. They aren't paying the commission directly, per se. And some might read the fine detail that it's only 15% for landers, not 25%.
Potential buyers certainly might start questioning whether the domain is available elsewhere cheaper. After all, whether a 15% or 25% markup, they would have the right to question whether this is the best venue to use. So, perhaps they end up going elsewhere, and buy the domain at another place where you have listed it. That, of course, could now be a problem for you. Doesn't GD require that still that effectively a "finder's fee" needs to be paid by the seller. And, if the seller doesn't pay, then the buyer is asked to do so?
The landers may turn out to be a more complicated issue than currently being mentioned. Could this mean that you, as a seller, could end up paying in let's say the 5-10% commission for a sale through a different marketplace, but also an additional 25% to GD?