I think the problem comes from the biome system in Planet Zoo. The animal's temperature requirements are dictated by the biome, rather than individually set for species; this system is no doubt convenient but does lead to some gross over-simplifications. While the Bactrian camel is a domestic species, it does originally hail from the Gobi desert, and is well adapted to both extreme hot and extreme cold temperatures. The problem arises from the fact that the Gobi desert is a cold desert, thus the average temperatures do not correspond with the hot desert settings in the game. Frontier cannot change the desert temperature settings as this would lead to inappropriate cold tolerance for hot desert species. The most accurate solution would be to add another biome, the cold desert, but I can understand Frontier's reluctance to add "too many" biomes, especially if it would only include one animal. As an approximation they should add Tundra to the biome list for the Bactrian camel. While its not a 100% perfect solution, the tundra is technically a cold desert. (The tundra foliage however would not be appropriate for the Bactrian).
The bison is an easy fix. It is listed under savannah, for grasslands, however the temperature settings are set to the African savannah, not the North American Great Plains. The temperate biome should also be added to the Bison.
Based on the precedent that Frontier set with the Aquatics pack I have high hopes that they will be receptive to making these changes.