Same problem here, the first time I join the network it uses the old method and makes an GET to http://captive.apple.com/hotspot-detect.html. However, if I rejoin the same network a second time (without forgetting the network inbetween) it uses the new DHCP option 114 and opens the captive portal as described in https://developer.apple.com/news/?id=q78sq5rv.
erikssa3
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