>>7880676It's not consistent because they're rushed to produce a 22 page comic in less than a month.
But you know what is consistent? The fact that flat pink part exists in 93.3333% of the rest of the issue for dozens of comics by dozens of artists for over 20 years and is drawn without depth to this day.
Nevermind the fact the story establishes the fact it's just covering his head and isn't sending his head to a pocket dimension (hence the fact that pink part of the mouth looks so flat and doesn't allow the other side to be seen in 95.53% of panels despite the gigantic mouth).
So yes, you're right, it's not drawn to be an actual mouth. There's no cavity there and that's why he's drawn and written that way.
But some people can't admit they're wrong, because their doctors told their parents not to say no to them or they'll get more outraged over minor things... like toys and comics.