The relationship between diet, microbiome, and health is fascinating.
Another metabolite of L. reuteri is ergothioneine, which is hypothesized to be a "longevity vitamin"[1] by biologist Bruce Ames[2]. Plants and animals cannot synthesize it, only fungi and bacteria, but it is found in every cell in our body including in high concentrations in mitochondria. It appears to be important enough that mammals have evolved a specialized transporter for uptake of this compound (SLC22A4), and mutations in this gene are associated with Crohn's disease.
Low levels of it have been linked to cognitive impairment, CVD, even depression and sleep disorders[3].
Macros aren't everything when it comes to diet, there's a whole universe of micronutrient interactions ongoing in our cells every day. Since we are in a position of relatively near total ignorance, I agree that we should pursue food diversity by default.
[1] https://www.pnas.org/doi/full/10.1073/pnas.1809045115
[2] https://en.wikipedia.org/wiki/Bruce_Ames#Notable_awards
[3] https://www.nature.com/articles/s41398-020-0855-1