The thing that makes this different than Elvis sightings is that Kaufmann was notorious for playing tricks on his audiences. In a way, it’s very believable that he could have faked his own death, but part of me wonders just how long he’d carry out the “joke” before revealing it was all an act.
15 years or so ago I read a book that made the case that Elvis is alive. It had all sorts of reasons, facts, and tidbits... And it really was quite convincing.