Let's back up. Are we talking about Musa, in general, or only about descendants of Musa acuminate and/or Musa balbisiana? Although I never paid much attention to the appearance of suckers, I don't remember ever seeing sword suckers on other species.
In this photo, left to right, are suckers on my potted M. Basjoo, M. 'Little Prince' and M. 'Truly Tiny':
As you can see, the Basjoo has a water sucker whereas 'Little Prince' and 'Truly Tiny' have sword suckers. All were given the same growing conditions.