As rumoring is accepted, I'd offer that the "5 crew" may also mean
1. that there was a unfortunate typo on the web site
2. that the website editor counted Blasik as Air Force and thus erroneously as crew ("one of us"), as the website is for the 36. Specjalnego Pułku Lotnictwa Transportowego „Obrońców Warszawy", the unit of 101.
3. that Blasik had booked himself as one of the crew to "fly hours" to keep his license. The crew discusses something in the 1st version of the CVR transcript around and after 10:03 about a "four-star general" (Blasik's NATO rank?), which may hint to that direction.
Alternative 3 per se may not mean that he overtook command of the flight.