Yet another reason for privacy-conscious individuals to switch to iOS and a newer iPhone. I hate the walled-gardens as much as the next person, but Apple's stance on privacy and security is unparalleled in today's ecosystem.
Don't be so sure your $CURRENT iPhone does not do that. I am watching a screen right now where I see the probes from iPhones fly by (# tshark -i wlan0 subtype probereq). Seems less then other devices but still they're there.
Any indication this is still the behavior in Android 7.0 and beyond? What about in Pixel phones? The one first-party Google device used in the study was a Nexus S running 4.4.
>= 7.0 improved on these and its not longer aggressively looking for beacons, it uses a passive approach.