It's actually inaccurate. People search BEFORE they go. In fact, I can tell you the busiest tourism month in Greece is August. I've been there dozens of times and June is actually a pleasant (tho cool-ish) time to visit - no crowds. And the Greeks are still working (trying to make money to spend on their August vacations - when everything shuts down). Perhaps Airline charters would be a more accurate reflection. Altho I do not know where to source that data.