The breathing Seane Corn teaches in the video is gentle, deep and SLOW (but naturally so, not exaggerated)... She says at the start of the video after demonstrating the correct breathing:
"If you feel like your breath is getting short or high in your chest.. take a break. Stop. Do less. Do whatever you need to go back to that (slow) breath..."
I don't know if it's the "perfect" breathing for AF... but I couldn't describe it as "hyperventilation" in any stretch of the imagination.
Do check out GaiamTV if you're looking for tons of yoga videos for any level of ability or adrenal function (I do the easy ones after a crash and work up to harder ones gradually over a few weeks... like Vinyasa Flow Yoga 2).
Gotta run.. time to do Vinyasa Flow 1 now before lunch!