That's a good find that famous people are getting into FOSS (should be free as in freedom too). But it's really not a good thing that they spread a non expert speaking to the crowd.

Tier lists are meant to be mainly subjective and pretty relative to the person that made it. In that way Pewdipie could quote experts but in no case should make a tier list based on what he found the last weeks (I didn't fully watched the video so maybe I'm wrong and he made a big disclaimer)