grapplehoeker: "If there are no critters there now, then there isn't a spawn point.
However, that's for regular daytime critters."

I am afraid you are mistaken. Creature spawning is rarely automatic. I have passed through a small patch of Black Forest, perhaps 120 square meters, containing only ferns, firs, and boulders that had no creatures. Less than five minutes later, a troll spawned in that patch. It was not "The Ground is Shaking..." event. I had no base structures within a several hundred meter radius.

In the Swamp I have stumbled across those high points containing boulders, two body piles, and an evil pile of bones. No skeletons or draugr were present when I got there. They did not start appearing until I attacked one of the body piles.

Creature spawning depends on RNG. The fact that no creatures are present at any given time in any given location is not an indication that there is no spawn point.