If you lay in the bed, depending on if you are lying on your back or stomach, left and right still change.
Ususally a bed is positioned with the head against a wall, so if you are facing the bed from the foot end, left and right are always the same. So I vote left/right is as seen from the foot end of the bed.
Sounds pretty similar to me and my grandparents, especially the part about not being vulnerable with each other. Mostly it’s surface-level talks. For example, my grandpa is into plants and gardening, so we might talk about the garden or his most recent visit to the garden center or something.
And I’m pretty sure behavior like this is passed down through generations.