If it's any consolation, they are full of shit. In the second jhana and above, the factors of initial and sustained attention disappear. In practical terms, this means you cannot direct your thoughts away from the object of concentration once you enter such state. You have to decide beforehand how long you will be in that state and give yourself a mental timer. See Dipa Ma's biography for a case of someone actually entering higher jhanas that way.

This is the reason that anything beyond the first dhyana is not encouraged in Mahayana, as it is impossible to apply vipasyana in a state of concentration so deep that you cannot direct your mind.

The teachers popular in the SF scene are inflating their own achievements and the ones of their students by using very lightweight criteria. I had that experience when I attended a TWIM retreat before their founder died. According to them, I reached the fourth or fifth jhana. I can assure you I did not.