Thank you so much! I found something similar to your explanation but was unable to prove it with blender but this one worked like a charm. Here are the results so that you may be more sure:
I put a cube and a plane in a scene. The cube has a floor constraint targeting the plane. I loc key the cube, move it down (with no visible effect because of the plane) and key it with a loc at frame 11. When I delete/move the plane the cube does a different animation (moves down to it’s target position if the plane is out of the way)
I do the same thing but instead using visualloc. When the plane is gone the cube just sits still during the animation because that was it’s visual position.
However, when using loc or visualloc neither one betrays the constraint, so if you move the plane up the box will never go below so the constraint stays true.