I don't think the stripe down the back has anything to do with the dog's temperament. Certainly I've met plenty of anxious and fearful dogs (including my very own muppet of perpetual terror!) who didn't have a bitch stripe.
ARCHMX TDCH Pongu the Insane, CD-C, RE, RL1X6, RL2X5, RL3X2 (GSD mix, b. Apr 2010)
Crookytail the Tigerwuff, RL1, ITD (Akita mix, b. Jan 2011)