I have no idea, but the switches you say work on the command line aren’t the ones you are trying to use in the actionscript.
You say this is the command line that works:
setup64.exe -s -f1c:\Users\public\Inst_Temp\PDDC5.0.6.1140R1\PDDC5.0.6.1140R1.iss -f2C:\ProgramData\DSE\Logs\PDDC5.0.6.1140R1_EXE.log
but that isn’t what you are doing in actionscript, you are doing the following:
setup64.exe /install /quiet /norestart /log REBOOT=REALLYSUPPRESS AllUSERS=1 /L*V C:\ProgramData\DSE\Logs\PDDC5.0.6.1140R1_EXE.log
These are not the same.