Nile Monitors need a lot of Space, so it makes Sense that they included it as a Habitat Animal. The Enclosure for 2 of them should be 400x200x200m (in Real Life)
In centimetres that is still smaller than the current in-game exhibits. 12m squared and 2m tall would basically be like halving the height of the in-game exhibit and adding that half onto the length and width.
@Bearcat9948 if I was to guess, I'd say the difference is in mobility. Monitor lizards are typically more active than iguanas, especially in captivity.
In any case I don't object to a slightly larger exhibit in principle, but I think smaller exhibits are a bigger priority based on the range of species we have. The iguana, boa, and anaconda are all perfectly fine in the current exhibit size, but the poison frogs and especially the tarantulas and other invertebrates only need a fraction of that space in real life. There would be visibility issues of course but with those tiny animals visibility is already an issue regardless, and since we have infinite zoom (pretty much) not much would really change in terms of that problem.
I'd like to see stackable 1x1 exhibits for these tiny animals. In theory you could display 16 different species in the same amount of space it takes to currently display one. That said to keep viewing at guest level I'd halve that number to 8 but it's still a good idea I think.