Well I mean, if you know a way to make minecraft about 2000 blocks tall or make trees less than 2 blocks tall.... Honestly, he's done pretty well scale-wise already.
Most of these are roughly around that, at first glance. Those 5 blocks aren't gonna make a big difference. Though perhaps they could've been sunk into the ground a bit more.
They are very tall. (The trees) and at that it seems he didnt use all of the space to 250 blocks but started on about 100 blocks so having only 150 left.... Minecraft isnt good for oversized buildings or structures (talking about the trees) in case you want to make them tall.. . The hight limit will always get in the way. And if you try to make mountains with 40 block tall structures in front of them they begin to look more like hills.
That is impossible to properly resolve anyway, so I've always been of the opinion that trying to get 'realistically' scaled mountains is an exercise in futility so you might as well go with it and just go for trying to get the best possible mountain shaping and coloring, and screw the trees.
Honestly, he's done pretty well scale-wise already.