Apple is really big into custom proprietary WiFi protocols (see also: AirDrop). So while AirPlay was originally limited to the local network, it now also appare

Apple is really big into custom proprietary WiFi protocols (see also: AirDrop). So while AirPlay was originally limited to the local network, it now also apparently works over WiFi direct - and presumably that requires some sort of WiFi scan, in turn requiring the radio to switch channels which causes latency to tank.