Meaning that no one is/has been challenged to "put up" unless they've made a claim?
Good to know...
Well, I'm sure it's happened, but I can't think of any examples.
Graham has certainly made voluminous claims but has never backed any of them up.
So he gets called down a lot....
And then there are those who say only what they can prove, but they're disputed by someone with no real basis for dispute: "You can't really do it" though hundreds of people know they can.
That's another kind that gets heat.
1) saying you can but refusing to back it up
2) saying someone can't when they've proven repeatedly that they can
But both are kinds of claims...