When your bed is destroyed, it does not say 'Your bed was missing or obstructed' when you respawn.

If sleeping in a bed resets the spawn point don't see how that would be a problem. Otherwise wouldn't it be game over if you can't respawn cuz the bed was missing or blocked? Or did you want it to revert to the original spawn point when the world was first made?

Nothing about this behavior indicates that it's a bug (it doesn't seem to be accidental). If you think the behavior can be improved, file it as an improvement instead of a bug...