For me the issue is the amount of stone required to make bricks. Carpenters benches get materials and crafting time reduced with thralls for every thing they make including insulated wood. The “hamburger helper” of oil for insulated wood is just make work. No real cost, just having to stand there and manage the limited space on the bench instead of playing.
Smelters get the time reduction but not the material cost reduction.
I don’t run an encumberance build and resetting my feats every time I want to mine the stone to make more than 15 t3 brick building pieces is not fun gameplay.
It makes the dlc less desirable for one thing.
On that subject, why does Khitan use so much brick instead of wood? Looks like wood to me.