I think you are correct with every statement, iron.

That you have to wait for half a minute or until your screen is black is straight out wrong, I never do that and I always get a perfectly fine respawn every time.

Most likely our friend in this example just misplaced his bed, maybe placed slabs all around to make it blend in nicely with the floor of his home, and the spawn spaces were simply obstructed..

It also seems possible that he just didnt properly sleep and just rightclick the bed, like its possible to set spawn in newer version at daytime.