Help explain what's happening

I don't have a photo to offer bc it's basically a behavioral thing, and i don't know if it's just a GX7 or all Panasonic or even all ML. So here's what i notice. When i shoot in A mode, with exposure preview set to ON or OFF, the LCD/EVF will change their gain (brightness of the image i see) even after AF is locked, even though exposure settings are also locked in with AF. Ok no biggie, at least i know the exposure of the shot will be what saw upon focusing.

Problem is, when focusing while the screen is darker the AF doesn't seem to lock. When the screen is brighter (ie when SS is longer), it does. I first noticed this when i had a very bright BG and my subject would dimm in the screen, it would have trouble locking. So i started playing around with exposure comp to force exposure to be brighter and sure enough, it locks perfectly fine when my would be dark subject is overexposed. Without moving the camera away i change exposure comp from +5 to -5, watching my SS shorten and the subject darken on screen, and the AF won't lock anymore.

It seems as if the AF system is dependent on the exposure settings (SS for sure, not sure about ISO), which i wasn't expecting. And, it only happens in A mode, in manual exposure and SS mode when the AF engages it seems to revert to a default exposure value just for AF. The camera sensor seems to "see" differently in A mode than the other two, applying the set SS exposure value while it's focusing.

Anybody else notice this, is it on other cameras too? Any staffers with DPR happen to know about this?