The most likely reason for you not being able to use the name is because the owner/maker of that syrup has let Ebay and other such sites know they will issue a cease and desist based on their ownership of the trademark “Aunt Jemima”.
Looking at all the ones currently on Ebay, I think you’re right. They all say, ‘Pancake Syrup’ in the listing; even though Aunt Jemima is pictured on the image of the bottle, the name of the product isn’t used.