If you can trust in one thing then it's people being around who don't.
Of course this entire thing will only affect Helryx, Artakha and Tuyet (as far as I've understood it). The thing is, though, heads are important, the most important thing in a MOC. So I'd expect a good-looking head/mask, even if one knows it won't become definite canon, to still subconsciously influence votes. A good head can distract from other things enough to influence the average voter, I believe.
From what @Racie02 just pointed out again, I kinda find it unfair that regardless of what the MOC does, the drawing will be the definite canon, though. Like, I'm not against 2D artists also be given a chance to do something, but if the most important part of the MOC isn't defined by the MOC, why even build a MOC?
Of course you could again say that an artwork keeping relatively close to the MOC's head design might have better chances due to it feeling more familiar, but basically there are only two outcomes here:
a) MOC and artwork look completely different (at least on first glance a simple head design will manage that) - why have a MOC then?
b) MOC and artwork look similar - why have artwork then?
Honestly, rules for this contest could be so simple - only MOCs, only official unmodified Lego parts, go.