If, as he suggests, it may be happening on iOS as well then it would offer third parties the interesting possibility of "probing" some locations for iPhone phot

If, as he suggests, it may be happening on iOS as well then it would offer third parties the interesting possibility of "probing" some locations for iPhone photo events, especially if the background requests and their headers can be distinguished from intentional requests. Say you own a bar, nightclub, popular tourist location, or whatever. Place specific QR codes at locations of encoding URLs pointing to a server you own, and you will be able to count how many times an iPhone user took a photo that included said QR code (or, if background scanning is active even before the picture is taken, how many times an iPhone was pointed towards it). Not that this would likely provide any valuable information for a malicious actor, nor could it really be done covertly. It's more of a thought experiment.