Actually, Frontier has done a good job keeping the new non-media animals at their correct sizes, and they even scaled down all of the non-media animals from the first game. The Dreadoughtus (original) and Alamosaurus have the opposite problem, they're a little too small compared to their real-life counterparts.
For the herbivores yes. For the carnivores, no. A lot of them are still oversized. The Albertosaurus is too big. Even the Ceratosaurus is huge, much bigger than it's JP3 inspiration, for reasons I'm not sure of, and like double the size of the actual animal.
The reason I think that, if there's a Woolly mammoth, they might over-size that is because Woollly mammoths weren't actual all that big. They were no bigger than Asian elephants. So people might not like that the mammoth is smaller than a Triceratops, even though in life it was. If they upscale it a little bit it should be OK.