At this point, inquiring minds want to know!
I can add to the mix that -as far as i know- there can not be a combination of grossER and Mercedes. Ein (a) grosses mercedes, das (the) grosse mercedes, das grossere (bigger) mercedes, ein grosseres (bigger) mercedes. It never becomes "grosser mercedes"
My money is on the yankees. General knowledge would allow for those people to know that gross is big. One syllable each.
But, they all heard "grosse", 2 syllables. So, English must be "bigger", 2 syllables as well, as a default, for big-ge does not exist to pick from.
OK, where's my Retalin?