Any one point alone is probably not sufficient to disprove an investment thesis. If the company fails on several points, then I think we need to be a bit circumspect.
However, I do not know of many companies which have not demonstrated an ability to generate +ve FCF over a long period and yet are "gems". Companies create value by generating sustainable FCF. I am kinda new here and not aware of the Valuepickr gems that you are referring to.
Thanks.