If an orc has sneak from a ragged cloak or whatever, even though they can hide and sneak in swamps at night, caves, and the orc village, if they transition between any of the terrain types they are pulled out of hiding, even though they can hide and sneak in all of them. Seems like they should just sneak right along.

The same is true of assassins going from forest to forest, for example, even with sneak.