The bug
When multiple configured structure features with the same type are referenced in a biome's starts, only one of them generates. For example, it is impossible to have both taiga villages and desert villages generate in the same biome.
How to reproduce:
Download the attached data pack
Create a new world and import the data pack. It will replace the overworld with swamps and attempt to generate all types of villages in the swamp biome.
Locate villages at different positions with the following command:
execute positioned ~3000 ~ ~ run locate village
Only taiga villages generate.
Note: in the pre-releases, the last feature of the same type would always generate, meaning that only plains villages would generate. This seems to have changed in 1.16.2, as I now only get taiga villages.
This is a major issue for datapack makers as they are using the Village and Bastion Remnants types to generate their jigsaw structures like castles or volcanos and stuff. However, due to this bug, these datapack makers cannot add 2 of their completely different structures to the same biome because they both uses the village type structure as the base of their configured structure.
While it may be a far long while before Mojang allows us to make completely custom structures by json, fixing this bug would greatly help as a workaround to allow datapack makers to generate many kinds of castles in a single biome instead of only one. (Although they could abuse multiple starting pools to bypass this limitation but then they lose the ability to control spacing for each structure)