Imagine all the previous people in that position that were incapable of properly doing their jobs because they had no Blackberry in which to receive secured information.
Imagine all the previous people in that position who were incapable of properly doing their jobs because they had no fax machine with which to receive secured information.
Imagine all the previous people in that position who were incapable of properly doing their jobs because they had no telephone with which to receive secured information.
Times change, and so does the technology required for the position.
Honestly I suspect their policy is "no wireless devices within the SCIF period." From wireless keyboards, to cellphones, to WiFi, and beyond. The black phone might be authorised but I suspect that is due to operational importance (e.g. calls vital to national security).
https://www.bostonglobe.com/news/nation/2015/09/30/john-kerr...
Would you be able to be good at your job if you were only able to check email once a day? I sure couldn't, but 15 years ago that's how often I checked it.