The Shadowed Belt Clasp for Blacksmithing recently had the Stonework specialization added to it in CraftSim, but Stonework does not affect the Shadowed Belt Clasp. CraftSim is taking Stonework's skill contribution and multicraft bonus into account in simulation mode as well.

When testing in-game, putting points into Stonework does not increase the crafting skill of the Shadowed Belt Clasp, or the multicraft chance. I also tested with 1000 crafts on the 10.1.5 PTR with 1/20 Stonework and 1000 crafts with 20/20 Stonework. The results were 1286 total belt clasps with 1/20 Stonework, and 1240 total belt clasps with 20/20 stonework, suggesting the 50% extra multicraft bonus from Stonework also does not apply to belt clasps.

See attached images for 1/20 Stonework and 20/20 Stonework on the in-game UI with no addons installed.

Oh, I assumed it scales with stonework because it's literally in the category called stonework. Do you happen to know what other node(s) it scales with? It definitely gets bonus skill from something but not sure from what exactly. Will try to fix it tomorrow as soon as someone figures out what affects it precisely

I was so focused on seeing the Stonework spec there I didn't realize there were others missing or incorrect.

My testing on the 10.1.5 PTR shows the following affect Belt Clasps: Armorsmithing, Fine Armor, Belts, Hammer Control, Safety Smithing, and Poignant Plans.

Specialty Smithing does not affect it.

Ah, so they count it as a belt, nice one blizzard, I got baited hard by them putting it in the stonework category next to all the items that scale with stonework lol