I think Fable means the "Fire Arrow Proficiency" type skills, which increase your damage when using a specific type of elemental arrow. I hadn't realized those were ever going to be important -- the increased damage from Bow Mastery is insulting (+8-12 for the first point, then like +1 every point thereafter), so I blew off the elemental arrow proficiency trainer when I saw him.

You will rue the day you opposed me! Begin your rueing! I'll just... sit over here... and watch.