I would love to see this same analysis with a gut probiotic! I am never convinced if I'm wasting my money, which strains are best, should I do refrigerated or shelf-stable, etc.
As far as I am aware, fiber has infinitely superior research behind it with far more drastic effects. Just take fiber if you're worried about gut health imo.
Anecdata/placebo/whatever: I use BioGaia's Gastrus tablets and they increase my quality of life noticeably, and I can tell when I've been off them for a while. I got refrigerated deliveries of probiotic yoghurt drinks for a while previously and in addition to the faff, didn't notice as good results.