Google On Ideal Number Of Products On A Page In Context of Ranking

Google’s John Mueller answered a question about how many product listings on a page are recommended as optimal for ranking purposes. 30 products) on a page because offering many products is a ranking factor? How Does Google Approach Usability Testing? In terms of ranking the SERP’s, what does Google prefer or what do you recommend? Or does Google look to conversion rate in the end to decide which category page (shop) deserves a top spot in the rankings?