Two prudent things to do when you see someone claiming to have insight into search algorithms -

Ask where they are getting their information. "A source at Google" doesn't cut it.

Ask yourself how much sense it makes. What is the likelihood that this could be a signal that improves search quality without causing significant collateral damage? Pretty low in this case.

I can think of plenty of genuinely high quality sites that do a horrible job with email. They probably send bad user signals through Gmail - but why should that impact web search? It shouldn't, and it doesn't.