Why do you believe them? Even if someone posts their photographs online, they could be posting someone else. I just read that testimonial and it reads exactly how I would imagine it would if Aajonus faked it to give his diet credibility. Not saying it's a fake, but it's the exact kind of tone and language I would think a fake would use. Actually I read a fake testimonial once, my ex girlfriend's dad owned a restaurant along with his brother, and online his brother wrote a fake review to make it sound good. It was blatantly obvious to me and I felt embarrassed for him and for my gf's dad. Lastly, I'd like to point out that if this diet is so great and this person so amazing, why would allowing anyone in the world to know about it hurt them? They're a leading business figure who somehow looks 30 years younger that we've never heard of, and they refuse to talk about why? The whole thing seems fake.
Well, it is vaguely plausible that he looks 30 years younger. There have been some famous people who've looked far younger than they really were, for genetic reasons etc.- with a good diet added in, there might be even further benefits.
As for secrecy, that's inevitable on this kind of diet. Raw meat diets are still frowned upon in the modern world so that celebrities are going to be extremely reluctant to promote such a diet openly. I know there are cases like Mel Gibson/Uma Thurman et al, who who eat our kind of diet, but they have a very good reason for being discreet about it:- one of the key things that celebrities worry about is being photographed eating foods as it makes them look odd/gross etc., which is why, at parties, they often sneak out into secluded areas(eg:- inside limousines) in order to eat standard food. I can't imagine any celebrity wanting to show himself eating raw meat in public.
Also, if you're a prominent businessman, the last thing you want is any kind of controversy even if you're doing something legal. For example, there are a number of respectable, law-abiding Mormon Fundamentalist businessmen in the US who practice polygamy in secret and who could really harm their business if they were revealed as polygamists - this, despite the fact that no State government dares, any more, to actually prosecute polygamy(instead they target other crimes that are sometimes related, at least with regard to the FLDS but not other groups).
I'm inclined to believe that most of the testimonials given by these people are genuine simply because the Primal Diet is thriving in the US(despite the numerous issues involved re dairy but anyway..) of course the very first testimonials given are likely to be bogus. It's quite common, for example, for newly-started magazines/journals to have completely fake readers' letters for a while before they build up a sizeable readership.