User blog comment:Xilinoc/Ch. 553 - Frozen Cross/@comment-1747976-20131020025317/@comment-1268838-20131020034328

I think that the easiest explanation is simply that all reishi particles are identical. Once Ayon was broken down into raw material, he was no longer a Hollow. The change to Quilge's form was merely cosmetic, and he became more powerful because that is what reishi does for a Quincy.