I think what Colan was describing was a dislike of illustrating certain genre stories, in this case fantasy. As an artist I can fully relate as I would do fantasy and sci-fi all day over street level stories. As much as I love Spider-Man, drawing endless city backgrounds would make me want to eat a bullet. I'd much rather do mysterious and atmospheric environments like in Namor or Dr Strange stories.
As for the triangle head topic, I can see what Thor-El is saying with later Everett work starting to elongate Namor's head, but he still illustrates the hair as hair, it's wavy and round. The truly weird alien looking Namor came with the later artists. I actually quite like this look of Everett's Namor and I feel Alex Ross is referencing this style of Namor for the Invaders homage cover painting he did where the giant Namor is smashing the Nazis. It's different than Ross' usual Namor where he's using the same reference model as his Captain America and Superman.