Mannatech is a commercial cult that is using an illegal pyramid scheme. The fact that this company, like all cults, patrols the internet for unfavorable testimonials and reviews, and pays its reps to shut critics up with fictional praise says a lot. All "testimonials" used in this company's marketing are paid for narratives.
A scientific rule goes as follows: personal anecdotes are not facts. Mannatech's advocates have a lot of emotion, and a lot of anecdotal "evidence".