If an air purifier review site is publishing research on their search traffic and affiliate site rings, I feel it's safe to say that their specialty is in seo, not air purifiers.
Everything is like this. If you want to sell a nonzero quantity of a generic product, you have to be an expert in advertising and SEO.
I think that's unfair. They could've hired someone to analyse this, or maybe it's just run by people who work other gigs too. I can post about dance and in-depth http traffic optimisation - people know more than one thing.