Do we know what categories a website to be part of the 'safe browsing' list? Did the author confirm that his similarly designed mastodon server was the culprit

Do we know what categories a website to be part of the 'safe browsing' list? Did the author confirm that his similarly designed mastodon server was the culprit or just a hunch? I didn't realise Google safe browsing extended beyond google products. In a way, it makes me think about what other products have ties in to google.