Not quite. There are 3 climatically extreme Biomes in vanilla. Mushroom Island which is extreme Ocean, Mesa which is extreme Desert and Ice Spikes, which is an extreme Ice Plains biome. Those Biomes are the end of the Biome Generation Chain and are created close to their slightly less extreme Counterparts. If you have for example an Ice Spikes Biome, you can be 100% sure there is an Ice Plains Biome next to it (even if that is small in comparision with the others around it). Since they are the End of the Biome chain, they have the lowest chance of spawning, because they can only be generated adjacent to one special Biome (what doesn't mean that it cannot be next to another Biome as well, I had a Savanna right next to Ice Spikes, but it was still adjacent to Ice Plains).
Speaking from personal experience not statistics. I went exploring for 3 hours and found 6 different mesas and an ice spike thingy.