Board Thread:General Discussion/@comment-30158106-20161006152256/@comment-9605025-20161006214858

Saftzie is correct, this is better suited for the Yu-Gi-Oh wiki. However, the answer is no. Fusion summoning is a form of special summoning; independent of the concept of union monsters. Defusing a fusion monster is like unsummoning a normal monster; it can only be done by a card effect such as De-Fusion. Note that union monsters also work differently than Vylons and Inzectors. Unions and fusions are 1st generation mechanics that are similar but also different from other mechanics such as Synchros and Xyzs. If you still want to know more, I suggest you ask on the Yu-Gi-Oh wiki.