Dripstone caves below y=0 do not generate copper ore

Bug
Dripstone caves above y=0 generate copious amounts of copper ore, making it the best biome to obtain it in mass quantities, similar to badlands gold. However, dripstone caves below y=0 do not generate any copper at all, which defeats the purpose of going there to gather copper.

Reproduce
Seed: 9030307658990181730
Coordinates: 4528 / -19 / 483265

Expected Result
Dripstone caves generate copper ore at any height, because that is one of its main features.

(Note: Blobs of copper ore generate within the stone to deepslate transition layers, but not beneath)