My experience with using the stop lever to shut the engine off (first oil change I did, I broke the line going from the vacuum pump to the brake booster, resulting in no vacuum for a week before I got the new hose from Fastlane)is that pushing it in slowly will do just that - make the engine idle real low to the point of stalling but not actually shutting off. I found that shoving the lever to off quickly and very firmly (almost hitting it more than pushing) will always kill the engine. My guess is that this is normal.
