I don't know, I think a stronger narrative for rangers is "survivalist", independent of any specific terrain. I think they're the only class who's abilities are location dependant. They shouldn't be.
My idea that I took forward into my take on the OG Natural Explorer is that you get both universal traits and terrain specific ones, with the caveat being that you only get one Terrain, which in this context is more than enough.
An
Open Sky specialization for instance would be Prairie/plains focused, and its benefits would gear towards a mounted playstyle, buffing mounts for you and your party and enhancing the use of mounts in and out of combat.
But then on top of that, the base ability
Call of the Wild itself confers universal benefits, enhancing yours and your parties ability to engage with any particular terrain.
You could change these, with effort, but the idea is that if the party wants to stack these, they'll need multiple Nature classes (Ranger, Druid, Beast Master, Hedge Mage) to do it, as all 4 share variants of Call of the Wild and, thus, terrain specialization.
Its a fair bit underbaked atm, as my game has morphed considerably from what it was when I originally set it down, but the basic idea is still there.