@The:
I tend to put www.apple.com in as a host name passthrough. Works fine then.
This could be one of the ten or hundred different URL's hard-coded in iOS.
When you have the change the random "www.apple.com" is used, the iOS thinks it is connected to the net …. and the pfSense Captive portal will still block the portal client to visit any other site
Just wire-shark your portal connection, you probably will not even find a "www.apple.com" (DNS) request .... so why allowing it ?