The Bug
Windswept Gravelly Hills & Windswept Savanna (known as Gravelly Mountains and Shattered Savanna in 1.17.1) aren't apart of the "Adventuring Time" advancement
Reproduce
Reproduce
Load a single biome world with Windswept Gravelly Hills or Windswept Savanna
Do /advancement grant @s only minecraft:adventure/sleep_in_bed
Open your advancement screen
❌ Notice no biomes have been unlocked under Adventuring Time
Expected Result
The biomes would be apart of "Adventuring Time" advancement
I can confirm this behavior. This ticket relates to MC-238966.