The baby_pokémon tag violates TWYS. It is a classification not unlike "ghost pokémon" or "bug pokémon" (which have been aliased to pokémon), and is treated as such with implications from various pokemon species, with the wiki stating:

Baby Pokémon can be of any age, since they do not grow or change in appearance until they evolve, which can be delayed indefinitely.

Note that this tag is NOT to be used for Pokémon that just happen to be young, and is specifically for those categorized as "baby Pokémon".

It is based solely on lore/outside information, and says nothing about how they appear. It results in posts such as these getting tagged with baby_pokémon despite the characters not looking young, and I could imagine some artists not appreciating their adult art being associated with "baby" tags when there's no babies or young-looking characters depicted.

Should the tag have its implications removed, and either moved to the Invalid category or aliased to the base pokémon tag?

My vote's for aliasing it to pokémon, like the other examples you mentioned.

Or making it automatically change to baby_pokemon_(lore)

I think it should go the same way as ghost and bug Pokémon, and get aliased.

But if we get a baby_pokemon_(lore) tag, I think we should also have one for the types.

faucet said:
But if we get a baby_pokemon_(lore) tag, I think we should also have one for the types.

And there's the slippery slope. If we make it a lore tag, then there'd be no reason to not do the same for every single other series and their own categories.

+1 for the alias-tuck
-1 for _(lore)

Baby Pokémon are barely visually or thematically coherent with each other and I don't see the practical utility.
Not to mention in recent months there's been pressure to step away from using species tags to meta-categorise species which don't share required genetics/anatomy or groups which aren't intuitively cohesive.

Mods should just nerf baby pokémon so that they are balanced again

If the issue is the connotations due to the word "baby" in the tag, why not call them something such as "pre-eveloutions" or the like?

binagon said:
If the issue is the connotations due to the word "baby" in the tag, why not call them something such as "pre-eveloutions" or something?

That'd be a fan term (and not one that seems to be commonly used), it'd get mixed up with non-baby Pokemon, and there's still the issue of why should we have the tag at all?

The term "baby" for Pokemon was, for a time, used in the trading card game, so the arguments that it's a "fan term" don't hold up. In modernity, they're given the "Baby Evolution" ability rather than being called "Baby Pokemon", but there is still a clear classification.

We also have legendary_pokémon despite that tag breaking the same rules mentioned in the OP.

It is based solely on lore/outside information, and says nothing about how they appear.

lafcadio said:
We also have legendary_pokémon despite that tag breaking the same rules mentioned in the OP.

I mean I want to get rid of that too, so ¯\_(ツ)_/¯

While we're getting rid of pointless Pokémon meta-tags, can we dispose of regional_form_(pokémon) and gigantamax_pokémon too? And the mega_evolution tag should only apply to images that actually show a mega evolution taking place, similar to the evolution_(transformation) tag.