I've occasionally heard anecdotes like this but I have a hard time imagining how this kind of thing ever happens outside of very small population centers with less than ten tech employers. Unless he's some kind of executive where huge amounts of resources are devoted specifically to vetting and networking is the interview process, what incentive is there for people in charge of hiring to share such granular info with one another? Is everyone in charge of hiring at major tech companies just in a big whatsapp group exchanging dirt on employees they didn't like?