Preferences are general. If you (q)uery the workshop, the kid will mutter or sketch or scream about whatever they need. If they're muttering something in Dwarven or working furiously, they've already gathered what they need.
You can check what they've already gathered with (t). Compare the materials they need with the materials they've gathered, and try to figure it out.
Preference-specific materials work only in the following ways:
1. If the kid has a preference for any kind of shell, they may require shell for their project. It doesn't have to be their preferred kind of shell.
2. If the kid has a preference for any kind of cloth, they may require cloth of the same subtype for their project. So a moody dwarf who likes llama wool will accept sheep wool, but will not accept cave spider silk.
3. If the kid has a preference for any kind of glass, they may require raw glass. If you have never created items of clear or crystal glass on site, they will use green glass. If you have created items of clear or crystal glass on site, you better hope you have the materials to make a piece of raw clear-or-crystal glass.
4. This isn't applicable in your situation, but if a moody smith has a preference for a type of metal and you've smelted that metal on-site, they will demand that metal as the base metal of their item. This applies until you smelt your first bar of adamantium, after which they will demand adamantium as the base metal of their item - no exceptions. (Which sucks if they end up making a mace or war hammer).
Types of rock, wood, gem, and bone are pretty much interchangable for moods.