Thanks for commenting Janine :) I agree, no one situation can be accurately judged and known by a generality. This is meant to be a quick guide of clues that a participant may not be being fully honest. As always, more probing is needed in each case to come to a full determination.
And I don’t mean to say participants are intentionally or maliciously trying to give false or unnatural data most of the time (though it does happen). Just saying often times people may not always feel comfortable being completely honest and natural and may fudge a little or exclude some pertinent information or something along those lines. As for being presumptuous…I see that as my job. I wouldn't be a good researcher if I believed everything I heard and saw at face value ;)
But your points are valid, and actually related to the next UX research article I’m working on, on why people may not feel fully comfortable behaving in a natural and organic way. I’d love to hear any more reasons you may have, maybe via email, or another medium article to boot perhaps! :)