Clones MC-253417, although that report didn't document this specific behaviour of the bug which I personally believe Mojang should consider when closing that issue.

If a chunk has skipped 1.18, either by the world skipping that version entirely or never loaded when the world was on 1.18 and loaded again in 1.19+ versions, deep darks will not generate in places where it would have if generated newly in 1.19, hence MC-253417, but ancient cities still generates in places where it would have.
If it really is intended that deep darks do not generate in the chunks that skipped 1.18, it's still likely that the ancient cities should never be there if there's no deep dark.

To reproduce

1. Go to 1.17.1 and use seed 3134764715783923990
2. Upgrade that world to the latest version and run

   /execute in minecraft:overworld run tp @s 188.94 -34.44 10.53 89.45 83.93

Observed Results: There is an ancient city but no deep dark in sight.
Expected results: Either there is a deep dark that also generates, or no ancient city there at all.

I've reported this issue before in MC-255967, but I am making this new report that flips the expected results around after talking about it on the discord server, as I'm not sure if it's intended that there's no deep darks.