No overworld ore generation on single biome of nether type

There is no overworld type ore generation on any nether based biome for a single biome game. However nether ores are generated, such as gold, quartz, and ancient debris. I found this to happen on every nether based biome selected when creating single biome. See attached screenshots.

 

Steps to reproduce:

1. Go create a new game
2. World type: single biome -> customize -> select Crimson Forest (or any nether biome)
3. Use fill command or dig and you will see no ores are generated in the stone, however nether ores are generated in netherrack.