Han Dong had learned from Mr. Black White and through his conversations with Winry.
As long as the materials are available.
The Fate equipment or Chaos Equipment can be obtained by 'forging'.
Moreover, it is not necessarily less quality than the finished equipment; it might even be superior. Additionally, it can be tailored to one's needs... Of course, this also adds another forging process where it requires hiring a highly skilled blacksmith.
This is why during the completion of [The Return of the Clown (Surface Chapter)], Knight Cass spent all his energy points on the exchange of materials.
'Big Carrion Ghoul's Claw' and 'Black Feathers' are collected from creatures on the outskirts of the city.
The armor forged naturally belongs to 'Chaos Equipment'.
"Kid, the 'Chaos equipment' that you forge, coupled with my forging skills and the intermediate materials I bring out, will reach 'Excellent+' quality.