I'm new to LEM/SolarWind (2 days old to be precise) so my answer may be riddled with bad practices... In any case, like you, I just discovered that SoftwareInstall events are primarily MSI executables and was not in the least bit satisified ... Here's the rule that I've created to filter out exe runs (generally installs)... as you can see, it will need to be fine-tuned to your environment. Add as many conditions as you need to filter it out properly
All it does is display all process starts/stops that are not standard windows processes which start in Program Files, Windows, or the short-hand PROGRA~ directories. Hope it works for you
It appears that SoftwareInstall is looking for the MSIInstaller events, like 1033. If the installer isn't going to call the Windows Application Installer service, it'll throw different events.