Using landscape cloth/weed fabric to line the base of a raised bed does NOT convert it into a container. A raised bed becomes a container only if it has a solid bottom.

no

If we put rocks at the bottom of a container, that raises the perched water table to start at a level above the rock layer. If I put those same rocks under the soil in a raised bed, how could it not act in the same way?

If large rocks with huge gaps between them create a raised perched water table, then how could landscape fabric which has extremely tiny openings not also create a perched water table for the soil above the fabric? I just want to understand the physics of what is different in those cases.

@gardengal48 (PNW Z8/9) I think I understood those points in the last message already. I am focused on trying to understand the physics of why a landscape cloth under the soil in a raised bed does not create a separation barrier between the soil in the raised bed and the soil under the landscape cloth

If I were to put a layer of rocks between the ground soil and the soil in the raised bed, that would not create a perched water table above the rocks? If not, then why does adding a layer of rocks at the bottom of a pot raise the perched water table to start where the rock layer touches the container soil? Once you add the separation layer of the rocks, the two situations look the same to me.

Putting rocks on top of landscape cloth won't cause a perched water table in your raised bed. Landscape cloth is meant to be water-permeable, so the water will go through the bed soil, down through the rocks, and right on down through the landscape cloth. And since rocks want to rise and landscape fabric degrade over time, all you will end up with is a raised bed full of rocks and possibly fabric scraps.

IF you want to try making a raised bed into a container, you would need to line it with something impermeable like a pool liner, punch some holes in it so it has drainage but is not permeable, then fill from there. And still, no rocks in the raised bed, because even lined in this fashion the rocks aren't going to stay put and will start rising up.

What are you planning on growing that you think you would want to have a perched water table in a raised bed sized area?

"I am focused on trying to understand the physics of why a landscape cloth under the soil in a raised bed does not create a separation barrier between the soil in the raised bed and the soil under the landscape cloth"

Because landscape fabric is fully permeable, it creates no barrier. Or none of any significance. And ground soil is permeable as well, so a layer of rocks - also permeable - also creates no barrier. But a container is non-permeable...except for a few drainage holes....and pretty much a closed system as well so a PWT is virtually inevitable in a container. It will rarely ever be a concern with inground soil unless under the very specific conditions outlined previously.