Old ores can generate in deepslate area because in tuff generate old ores and tuff generates under y 0

Old ores can generate in deepslate area because in tuff generate old ores and tuff generates under y 0

What I expected to happen was...:
Deepslate textures should generate

What actually happened was...:
stone ores generate

Steps to Reproduce:
search under y 0 for an old ore