More likely that it’s the case that more bacteria in your stomach isn’t necessarily a better thing.
These negative effects have been noted in the literature, too, so I’m not alone: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6006167/
These negative effects have been noted in the literature, too, so I’m not alone: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6006167/
So whether the issue is too much bacteria or poor compatibly with a host remains unanswered by your linked study.