Mesa Plateau F M sub-biome redundant?

After exploring the different types of Mesa sub-biomes, I understand what's unique about all of them except for one. (This isn't an obvious problem per se, but I bring it up because I'm wondering if a terrain feature isn't working as Mojang intended.)

• Mesa is kinda low and flat.
• Mesa (Bryce) adds spires.
• Mesa Plateau is high and flat.
• Mesa Plateau F adds a bit of plant life.
• Mesa Plateau M has steeper terrain.

By the letters, one might expect the final sub-biome, "Mesa Plateau F M," to have both a steeper terrain and a few trees. Having visited several such areas after finding them in Amidst, however, I've found no plant life in F M (unlike F, which does have some), and I'm tempted to say the terrain looks actually very much like plain-old Mesa (low and mostly flat).

Is this intended?