A) It isn’t clear what role aerosols play in transmission, but it’s certainly not the only way the virus is transmitted. Large respiratory droplets play at least a large role, if not the clear primary role (the current assumption). Distancing helps, but of course masks help as well.
B) Just because some of the aerosolized vapors came through doesn’t mean some weren’t filtered. Even in the video, you can clearly see the difference between the medical/surgical masks and the cloth ones. The less virus that comes out, the less the ability to infect. Even if the masks just lower the momentum of the particles escaping (causing the droplets to fall to the floor or dissipate sooner, which is one of the reasons masks are recommended) but don’t actually prevent them from getting out, the potential to infect others is dramatically reduced.
C) Not all aerosols are created equal.
Masks and distancing *reduce* but do not *eliminate* transmission. That’s why people should wear masks, but not rely on them completely.