Sorry I can't set "20w07a" for the version, but I can't test this on the 20w08a because this Snapshot seems not to be available yet on my launcher :/

When creating custom recipes in Data Packs, we are able to use tags. They're defined in the folder "tags/<blocks|entity_types|fluids|items>" according to the type of elements it contains.

Minecraft Vanilla includes some predefined tags, including "minecraft:carpets" (each color of carpet) for example, or "minecraft:nylium" (the two types of Nylium). (See the attached files, taken from "20w07a/data/minecraft/tags/blocks")

When using the tag "minecraft:carpets" (for example), the craft works well. But with the tag "minecraft:nylium", it doesn't works anymore.

What I expected to happen was...:
This tag should works like other tags.

What actually happened was...:
Actually, the tag can't be used in custom recipes

Steps to Reproduce:

1. Download the Data Pack, see the files and notice that the craft using Nylium is not working.

OR

1. Create an empty Data Pack.
2. Add two custom recipes: one using the tag "minecraft:carpets", other using "minecraft:nylium".
3. Notice that the craft with the Nylium tag is not working.