Turning on broadcast SSID on AP allows AP to send SSID in beacon packets .
Beacon is like keepalive packets . Clients like XP , searches for any wireless
network in nearby area to connect to it . So for such clients it is useful to turn
on broadcast SSID . I guess your dlink also worked on same principle and got connected .
As SSID is transmitted in every beacon it is consider as security risk and document suggest not to turn on broadcast ssid .
SSID is NOT for security reason although many people consider ssid as security measure .
Even you turn off broadcast ssid in beacon packet by turning off ssid on ap ,
probe request and proble response will always contain the SSID . there is no
way to hide the ssid .
WGB does not show broadcast ssid as wgb is client device
thanks
Nilesh