In fact, the recent GMail got a feature to push old unreplied mails to the top (advertised for instance in https://www.indiatoday.in/technology/news/story/gmail

In fact, the recent GMail got a feature to push old unreplied mails to the top (advertised for instance in https://www.indiatoday.in/technology/news/story/gmail-redesigned-new-features-here-s-everything-to-know-and-how-you-can-get-it-1219719-2018-04-25 https://www.indiatoday.in/technology/news/story/gmail-redesi... ). I think Randall refers to this feature.