Hmmmm...you must have read different books than I did. Maybe (and I mean a big maybe), that could kind of apply to the movie versions of those characters, but that came out almost twenty years later.
I always felt that Flint was another attempt at comic relief, along a different vector than Tas. In addition to being the (overdone) straight man for Tas, he always reminded me of BA Baraccus from the A-team, a popular show at the time. He had had a similar issue as Flint, but with flying instead of boats. It was a running gag on the show that they had to sedate/knock him out every episode when they needed to fly. Zany attempts at comedy with irascible character.