Trial chambers wall dispensers' copper bulbs are always unoxidized

The 3 screenshots show that every single time a wall dispenser spawns in a trial chamber the only bulb type it has is the unoxidized waxed copper bulbs. The template_pool json file confirms that they do not have the copper bulb degradation processor (the one that randomly takes waxed copper bulbs and turns them into the exposed, weathered or oxidized versions).

Any seed works, but for example:

Seed: 2688
Coords: /execute in overworld run tp 176 -30 64

Observed result:
If you look through each chamber carefully and pay special attention to the copper bulbs behind the dispensers in there, you'll see they are all unoxidized waxed copper bulbs.

Expected result:
The copper bulbs come in unoxidized, exposed, weathered or oxidized versions.