The Bug

As of 25w02a, farm animals were made to be able to spawn in all Badlands biomes. Despite this, in practice, they only spawn in Wooded Badlands, as they're only able to spawn on grass still.

This change may seem innocent, but I assume that as a result of this (or perhaps merely a coincidence), in the normal Badlands biomes where only armadillos are actually able to spawn since they can spawn on terracotta, Armadillos spawn much less despite nothing else taking up their space.

This makes Badlands biomes feel extremely empty again, which was something the Armadillo had previously addressed.

Example Screenshots

Seed: -5853161135001706410
Coords: 596, 1211515

In 1.21.4:

In 25w02a:    

Note:
It's possible that actually, the bug here is farm animals don't spawn in non-wooded Badlands when they're supposed to, and it was just never updated to allow them to spawn on red sand/terracotta, but as that seems unprecedented I will assume the bug is armadillos spawning much much less by accident as a result of the spawning changes.