The Arrow Revolver skill was invented not by archers but wizards. The idea of loading arrows in advance came from charging Icebolts. For beginners, it would be challenging to load even 2 arrows due to the high tension of the bow string. Thus, loading 5 arrows and maintaining that state would seem mysterious and almost magical to beginners. Get the Fire Arrow title, then talk to Aranwen about skills (You may not have Any Advanced magic quests going on at the time). Then complete the book you get for the quest, turn it in, and you will get the skill.