Flat world preset code: stronghold not working properly

Like decoration (MC-188569), the "stronghold" tag no longer seems to generate strongholds in superflat worlds

How to reproduce

1. Create a new superflat world with the Overworld setting and add ";stronghold"
2. After loading, use /locate stronghold
3. "Could not find that structure nearby"

Original Report

Can be verified in a superflat world with a preset such as

minecraft:bedrock,2*minecraft:dirt,minecraft:grass_block;minecraft:bamboo_jungle;stronghold

and /locate command.

This also changes positions of other strongholds, due to how the generation works.

In the source code the two bamboo biomes are missing in OverworldBiomeSource.POSSIBLE_BIOMES .