Yes, there are some interesting potential mild modulations that can occur with microbiome change.

That paper commits one of the major sins of many microbiome papers which is to attribute all benefits of diet change to the microbiome. Like the parent commenter it gets drawn to the idea that all changes in the body can be traced back to the microbiome and assumes that it explains everything, but that’s obviously not true.

However, when someone is taking two powerful substances with direct brain action and known modulators effects on memory, blaming anything else in the body is bad logic.