You want to know why the wsusscn2.cab needs to present on all machines with the Agents installed and why this file needs to be updated.
LanGuard is using the Windows Update Agent (WUA) engine from Microsoft to detect missing Windows patches and updates. For this, LanGuard calls the WUA and provides it the latest copy of the wsusscn2.cab - an offline Scan Package.
For the Agents to perform scans independently and ascertain what patches are needed on the target machine, they need to have an updated copy of this file. Please, refer to Missing Patch Detection for Windows in the GFI LanGuard article for details.
Wsusscn2.cab is provided by Microsoft, and GFI has no control over its size.