John Mueller cleared this up in a Google Webmaster Hangout in
July 2018 with:
“We try not to use signals like that when it comes to search. So
that’s something where there are lots of reasons why users might
go back and forth, or look at different things in the search results, or
stay just briefly on a page and move back again. I think that’s really
hard to refine and say, “well, we could turn this into a ranking factor.”
Verdict: SEO myth
HOW TO SPOT SEO MYTHS: 20 COMMON SEO MYTHS, DEBUNKED