There have been plenty of woo slingers here who have insisted that the way to convince myself that their anecdote about, say, visiting a particular psychic is compelling evidence that he/she is genuine is to visit that psychic myself. No, it isn't, because I have the same cognitive biases and fallible perceptions and memory as they do. A carefully blinded scientific experiment is the way to convince me, and I wouldn't need to be present myself (let alone conduct it myself) as long as I was convinced the scientific method had been scrupulously followed.
The difference is not that the evidence is obtained by me personally but that it is obtained using the scientific method. Yes it's ideal if I can conduct the experiment myself, but that's not the essential part of how the evidence is obtained.