Not aware of anything from Apple about this issue. It was just an assumption, sorry. What I did is test up to date devices (i think i even tested an up to date iOS 6) and couldn't get any specific SSID. The probe requests were still there, but SSID parameter was always set to Broadcast.

However I did see a lots of probe requests WITH a SSID parameter set but those were not coming from my devices :). I assumed they were not up to date.

I am very interested to know if the probe requests you're seeing are also coming from unknown devices: if they aren't, could you provide us with the iOS version you're using/testing with?