Not quite...
Teragon biomes can easily be large rather than small, but it depends on your settings. For elevation based biomes, you need to create terrain that gives you good locations for higher elevations, which is possible.
Also, Teragon can easily generate different terrain and differently elevated terrain in each biome. The fifth default preset, Works Generator 5, does basically that, though it is not set up to give each biome a different elevation but instead gives different terrain for each. But it would work the same way. If you wanted, you could easily have Teragon generate each biome at very different elevations with very different terrain with cliffs or rivers separating them if that was what you wanted.
The main issue with such a map is having a way to get up onto that higher elevation, unless you just want to use gyros for that. Teragon currently doesn't have the ability to make switchbacks, so getting a road up the side of a cliff would need to be done by hand or else the road would look really odd.
Teragon can do a lot of things that you might not realize until you've used it a lot.