The fun part is that shop=cosmetics is not in a long tail. See Tag:shop=cosmetics - OpenStreetMap Wiki - over 32k uses, dedicated support in a few places.

If shop selling primarily/only soap can be correctly tagged as shop=cosmetics with some subtags then it can be useful to do so (though if it does not match well then doing this would be tagging for renderer).

And deciding on tagging one way or another (or at least giving hints) helps in mapping. Recently on train station I have seen shop-only shop, from what I remember I ended having problem how to mark it.