Could an Increase in Traffic Cause a Manual Review?

[aristotle]

Is it possible that Google keeps track of the total monthly traffic it sends to every website, and if the traffic to a particular site climbs past a certain threshold, it gets flagged for a manual review by a google employee to make sure that it is clean?

[tedster]

It's certainly possible - but I think more likely metric is a major increase in search results impressions for a domain, whether they are clicked on or not.

A significant increase in impressions means the algo has awarded higher ranking on some SERPs, and if any of those SERPs are the kind of "close scrutiny" SERPs that human evaluation keeps a look over, a manual inspection would be more likely.