Well, that's the thing, maybe Ron had zero input to the direction of the graphics for the first two Monkey Island games. We don't know for absolute certainty, but I wouldn't be surprised if that was the case.
Just look at the credits for MM1, it's a bit of a stretch to call it "his game". Yes, the original concept was his, but according to the credits, he did 33% of the coding, 33% of the writing, and 0% of the art and the music. So effectively he was one (important) member in a team of 20-30. But most likely it wasn't his decision to approve the art.
https://www.mobygames.com/game/dos/secret-of-monkey-island/credits
Oh, and
Falksi mentioned he couldn't believe this is the same guy who came up with the sword fighting insults. Turns out
that was someone else entirely (check first and last lines in his Game Credits section).