Input from your game controller isn't treated by the system the same as input from the keyboard or mouse. Specifically, it doesn't reset the idle timer.
At present, the only solution is to use 'Performance Mode' with your games. This will prevent IdleSaver from engaging while you are playing, assuming IdleSaver's 'Disable while Performance Mode is engaged' setting is ON (the default).
To do this, right-click on your game process(es) and select 'Induce Performance Mode'.
If you prefer Performance Mode not change the power profile, there is a setting for that in 'Options / Power / Performance Mode'.