I think I know where the miscommunication is here.
Major skills are what let you raise your character's level. If you have Blade as a Major and Blunt as a Minor, then raising Blade will help you to level-up, while raising Blunt will not.
However, you can get both Blade and Blunt up to 100, it will just take much longer to do it for Blunt. This seems to be a mix-up in wording.