When the IQ Remote PowerG is paired via PowerG, it will not have the silent disarm feature. Only the ones paired via Wi-Fi will.
A ticket has been submitted to Qolsys’ engineering team regarding the current issues I’ve noticed while on PowerG. At this moment, I don’t have any information on why Qolsys decided to make it available only on Wi-Fi or if they plan to support it via PowerG in the future.
If you have good Wi-Fi coverage in the area, you may want to try reconnecting that IQ Remote PowerG via Wi-Fi instead, which would allow you to use the silent disarm feature.