It’s OTC, I get it all the time (cat too)
Not single product is going to agree with every single animal (or human).
I don’t go by the majority of reviews online, as voluntary reports tend to be either overly good, or overly bad. I’d bet most people who use things like this don’t go reporting how well it worked, but they’re VERY happy to report how poorly it affected their animal
Amazon has 83% 5-star reviews
Chewy has 89% 5-star reviews
PetCo has 84% 5-star reviews
Clearly it works for 1000s and 1000s of dogs
Not all GI issues are a biotic issue, so adding something like this, for that, could potentially make things worse or, more likely, just not help. More, is not always better
Bentonite clay is also something that could be tried. I wouldn’t use it long-term, but if it stopped the problem, it could be a useful diagnostic