Found while reviewing eclipse-platform/eclipse.platform#2582.
Change ToggleStepFiltersAction to have constructor for better reproduction and add breakpoint in the constructor, as shown in the screenshot.
After ToggleStepFiltersAction.fInitialized value is set to false, hover over the ToggleStepFiltersAction.fInitialized to see the value.
It shows true !!! which is where you start to believe in magic, until you notice that the super class DebugCommandAction also has private field with exact same name but different value. OMG.
Obviously, debugger shows wrong velue on hover.