He’s really talking (mostly indirectly) about the importance of proximity to the subject—you need to keep some distance so as not to get unpleasant perspective distortion of facial features, and it’s this that makes a 50mm too short for anything closer than a three quarter length portrait. When he said the crop doesn’t matter, he was talking specifically about the 1.5/1.6 factor crops typically found on Nikon and Canon consumer DSLRs which don’t make that significant a difference to the perceived focal length of a 50mm when compared to the 160mm focal length he took the “good” example on. In other words, 80mm (equivalent) is still too short (many would disagree on that point). He wasn’t talking about the more extreme crop factors of typical compact cameras—if you had a superzoom with a crop factor of 5, zoomed it out to 32mm (160mm equivalent), positioned the camera the same distance from the model as he did with his “good” example and took a shot, the overall look of the picture would be about the same in terms of framing and perspective flattening. It’s the proximity that makes the difference, and choice of focal length is about framing. Knowing his ideal proximity to subject would have actually been more helpful than focal length… 
Either way, he seems to agree (implied) that a 35mm equivalent smartphone lens is too wide for a decent portrait shot. 
