I have the same problem and I did the same as you! I had 20w17a and copied the world, ran commands and found no ancient debris. I went and downgraded that copied world into 20w16, suprisingly there were ancient debris and soul biome generated (I couldn't find soul biome or ancient debris in the 20w17a). My issue is not solved, I have made a report. Can't downgrade the world without everything gone.
Thank you for responding. The issue is that there are missing details in the 20w17a for me. The soul biome and ancient debris in 20w16a are not in the 20w17a.
If you have explored a lot in the nether... Is all that loaded chunks?