Describe the bug
This issue is new to MC 1.21.4. It does not occur in MC 1.21.3, and sounds different from the baby issues mentionned in the pinned post.

Baby villagers can usually use the non-_baby versions of the villager models. However, if there exists is a villager.properties (even an empty one), then model n°1 will use the vanilla model instead of the regular custom model. Other numbered models seem to work fine.

For example:

# Both babies and adults use `villager2.jem`
models.1=2 
nbt.1.SleepingX=exists:true

# Adults use `villager.jem`, but Babies use the vanilla model.
# (This bit is implied, removing it from the file doesn't change the behaviour.)
models.2=1

List and link to broken resourcepacks
This is based on Human-Era-Villagers, but here's the smallest pack required to reproduce the issue: hev-debug.zip

Expected behavior

This is how the same pack behaved in MC 1.21.3. This behaviour can still be achieved, by renaming villager.jem to villager3.jem, and using these properties:

models.1=2 
nbt.1.SleepingX=exists:true

models.2=3

Alternatively, I'd need to provide identical _baby copies of both villager.jem and villager2.cem. (Providing a villager_baby without a _baby2 would cause the sleeping model to fail instead, but I believe that's expected in this case ?)

(please complete the following information):

• Minecraft Version: 1.21.4
• EMF version: 1.21.4-2.4.1
• ETF version if applicable: 1.21.4-6.2.10

Additional context
I'm not familiar with the Optifine format at all; me forking this pack is basically my first experience of it. I've skimmed through the relevant documentation, but please point out the obvious if I'm missing anything.

When using the option "show debug data on right-click", on 1.21.4, clicking a baby villager lists both the baby and the regular models. On 1.21.3, only the regular model is listed.