I think it’s quite possible to recruit subjects for observed testing. I don’t think it would work otherwise for the reasons you state and beyond that you’d have to ensure that everyone is using the same technique and experiencing the same forces.
I think you are right that the further outside your own experience someone’s gains are, the less likely they seem. I think that goes in either direction, it’s easy to wonder why people have purportedly done the same routine as you and gained nothing, when you’ve done it and gained well. Beyond that, you have to make the assumption that people are generally attempting to give a true impression of their experience or the entire idea of this board falls apart. There are definitely bullshitters, for reasons of financial gain, for their own enjoyment or to maybe attempt to fill a void in their psyche. It’s also fairly obvious that the larger the claimed gains the more chance that it’s bullshit but there are also outliers in any set.
I think this thread is useful, not for the stated gains of any individual but to see if there are trends in people claiming larger gains. It would seem sensible that if a large number of people have followed a similar path and they all claim better results than the norm, that it’s sensible to look at what they are doing. So far, I think commitment is the obvious commonality but beyond that the methods seem to vary wildly and so in some way this thread isn’t making a case for a particular approach.