He found out he bought a book about “chicanos” which I assume is slang for a gay or lesbian Latino/Latina person which the user takes as confirmation that the purchase they made in 1998 is the explanation for why they are receiving recommendations for Hispanic LGBT literature now in 2021.

I don’t think the user meant to imply they had gained any special insight into the algorithm other then personal confirmation that purchase as far back as 1998 are still being incorporated.

Chicano means a Mexican-American with political overtones.