there is nothing wrong with what he is saying
the company had some brilliant ground breaking idea of having a BOV that opens at low load/under vaccum, from memory it was for quicker throttle response, as when you crack the throttle, the air has a much shorter inlet path to the plenum, because intercoolers and piping and the whole turbo system is a big restriction.
the guy in the video is talking about that product specifically, because it draws in air under vaccum, people like to put filters on them. but hes saying that because the bimmer turbo is so 'efficient' and flows enough air, that there is actualy no vaccum through the BOV (again, keep in mind, this is product specific).
stupid thing is, if there is no vaccum though the BOV, there is no need to use their product on that car lol. that said it will probly open if you suddenly stab the throttle. i still found it funny though