Instead of using its own quadrants, Pedestal uses Slanted's.
This means that these quadrants never generate in Pedestal:
trial_chambers/chamber/pedestal/quadrant_1 (render from the Minecraft Wiki)
trial_chambers/chamber/pedestal/quadrant_2 (render from the Minecraft Wiki)
trial_chambers/chamber/pedestal/quadrant_3 (render from the Minecraft Wiki)
Instead, these will:
trial_chambers/chamber/slanted/quadrant_1 (render from the Minecraft Wiki)
trial_chambers/chamber/slanted/quadrant_2 (render from the Minecraft Wiki)
trial_chambers/chamber/slanted/quadrant_3 (render from the Minecraft Wiki)
trial_chambers/chamber/slanted/quadrant_4 (render from the Minecraft Wiki)
This might also explain why some dispenser traps are covered behind walls.
How to reproduce?
Use /place structure minecraft:trial_chambers until you find a Pedestal room
Look at the quadrants
Example of seed where this happens
-349722149179267981
/execute in minecraft:overworld run tp @s -917.15 7.61 3006.36 -223.63 47.78
Can confirm.