It's based on data gathered from scientific instruments that are well-characterized and whose results are validated by being used for other findings. They're not administering a questionnaire to someone's microbiome and doing sample statistics on the results. They found novel RNA sequences in microbiome sample data using well-understood and repeatable methods, and confirmed that the RNA sequences seem to exist. You can repeat the analysis yourself and make that determination.

I think you're trying to draw a comparison here between two things of completely different category, and I feel like you might not understand how different they are.