I don’t think father amorph himself goes by that exact definition of exorcism. You will find that out when you read the book. If a person came to him troubled by a demon, or a curse, or some sort of spell, if he fixed it he called that an exorcism. He says early on in his book that actual possession is very rare. Therefore in order for him to have done all those exorcisms he would have had to have had a broader definition for it.
That makes sense, and brings order back into my realm. 8>)