I could draw the face from that angle if I wanted, the mask is to add a further element of spoof to an already spoofy storyline.
According to my bottomless memory of YTOTW, I think I've only ever drawn YZ's face head-on in one strip. Ages ago, during the 'ganja in the stew' storyline, when he was sitting on a sofa watching TV.
Paul, meanwhile, has been pictured head-on in two strips. Surely some shameless favouritism there.