Actually I agree with his opinion, with one key exception. Almost all of the strains in Prescript-Assist are soil-based, which does mean they are not native to the GI tract and won't stick around. If these were the only strains included, I doubt it would affect my body the way it does.
But it also includes Bacteroides, which is not only native to the GI tract, it is the predominant genus of bacteria in the GI tract! Out of hundreds of species of bacteria in the gut, Bacteroides alone is estimated to account for at least 20% of all GI bacteria. No other probiotic that I know of contains Bacteroides, so this is why I choose Prescript-Assist - along with the fact that it has an incredibly dramatic effect on my candida symptoms, in a way that no other product has so far.
Now if you look at lactobacillus-based probiotics, they have shown some positive results in helping with GI symptoms. But if you look at studies like the ones I've referenced in previous posts, lactobacillus and bifidobacterium are very minor genera in the GI tract. Again and again Bacteroides is indicated as the leading GI bacterial genus.
That said, I do agree with you that probiotics have a ways to go before they match our GI tract microflora. A Fecal Transplant or "poop pill" would be an identical match, and likely contains hundreds of strains of bacteria. I suspect that before too long they will identify all of these and be able to manufacture an identical probiotic. Only time will tell.