I thought that repeatable, observable evidence is the way to assess whether any claim is valid. Of course, it would be more difficult to demonstrate that any claim is invalid because it would probably be claimed that conditions were not right.
If the purpose of claims are for pure theatre then fine as people pay good money to be entertained by make-believe which is more effective when a sense of uncertainty is introduced which would make it understandable that some would not wish to be put to the test.
Many of the best magicians prefer to illicit intrigue by invoking a "how the hell did he do that" instead of by claiming some sort of ability to suspend natural laws.
Naturally, in all or some of this, I may be wrong.
