Conducting modifications to a crafting furnace was a sort of convention amongst the circle of refiners.
Every refiner possessed their own unique methods and habits, so their requirements for their smelting furnaces varied broadly.
The Empyrean Terminus Sect was a sect that produced crafting furnaces such as these as their primary business. While they offered modification services of their own, they wouldn’t restrict others from modifying the crafting furnaces produced by their sect.
That would be equivalent to pushing business out the door.
However, there existed an enormous problem when one sought to modify their crafting furnace by oneself. What if the crafting furnace malfunctions after the modification? What if the refined magical equipment product doesn’t match the standards? What if it even causes a serious accident like the furnace exploding? Then who, in the end, would take the blame?