So after reading all the leaked material I'm 99% sure this is how planet exploration works.
- Each planet has certain parameters that the engine follows when you land on it. For example this planet is supposed to be brown and rocky with these creatures, these facilities, these caves, etc. (Now that we have more info, this matches with what Todd Howard said when they released the last Direct video showcase. That the planet generates points of interest around where you land.)
- when you pick any spot you want to land on that planet the game procedurally generates matching terrain and drops those items, creatures, facilities etc into that square of terrain.
- when you leave the planet and pick a new spot to land, even if it's right at the edge of the previous boundary you hit, the game just procedurally generates new terrain that won't match up with the area that you just left. Essentially this makes the whole idea of exploring a planet a lie. The planets are simply "gateways" to that planets predetermined map-type.
- Basically each planet has one map that is procedurally generated every time you land. This makes where you land completely pointless and, honestly, a marketing gimmick.
One caveat to this is that planets might have different biomes, like forest, desert, etc. The planet knows which biome is supposed to generate based on where you click to land. And then just follows the formula listed above.
Very disappointing.