G1X -- unexpected behavior in AEB mode while in Av

I noticed, what I consider, strange behavior today. With the camera set in Av and in AEB mode, the camera was changing the f/stop as well as the shutter speed. I expected just the Shutter speed to change. Any thoughts on what I did wrong?

The settings were: iso/800, f/2.8, AEB +/- 1.67.
The shots were taken at:
ev: 0, 1s, f/3.5
ev:-1.67, 0.8s, f/5.6
ev: 1.67, 1s, f/2.8

IMAGE LINK: http://www.flickr.com …44350103@N05/12​688500943/

IMAGE LINK: http://www.flickr.com …44350103@N05/12​688500923/

IMAGE LINK: http://www.flickr.com …44350103@N05/12​688845264/

IMAGE LINK: http://www.flickr.com …44350103@N05/12​687942293/

Safety shift is enabled.

Thank you!

I had looked at the AEB page in the manual and didn't see any thing. It never occurred to me that there was a safety built into Av; I had never seen anything like that on Av mode before.

So basically you got 2 functions for the price of one, focus stacking and exposure stacking.

Yes, the AEB feature has both exposure and focus staking (I haven't had occasion to try focus staking yet).

It is a pretty incredible camera. It has the serious stuff (Manual, AEB, etc.) plus stuff you'd expect to find on a P&S (facial recognition focusing, blink detection and a whole slew of things I haven't paid much attention to).