Scientists aren't 100% sure of what dinosaurs looked like but they're pretty much sure of how the head of the brachiosaurus looked because it had a very distinctive elevated arc between the eyes that is very visible in its skull. Queen's zoan doesn't have the head of a brachiosaurus because there's no way that flat forehead hides an elongated bony bulge.
What you're defending is more like accepting an spinosaurus without spine because "scientists can't be 100% sure of how it looked like". Well, of course to a certain extent, but Oda here is ignoring a well-known distinctive trait from a skull that is visibly present in virtually every good depiction, be it scientific or popular, of the animal.