Note they started adding the "interstate commerce" in there after the first version of the gun-free school zone act was found unconstitutional. Which then continued on to do the exact same thing when amended.

It's a distinction without difference.

Post Wickard v Filburn, mere possession of something has been found to be interstate commerce even if it's just a plant grown on your own property for your own consumption without ever entering interstate commerce. Note the controlled substance act depends on the same interstate commerce clause but they've upheld federal convictions for simple possession without showing any actual effect to commerce -- instead arguing that they've influenced interstate commerce by deciding to not participate in it and that if people did that in aggregate it would affect interstate commerce therefore it is interstate commerce. Complete madness obviously, but that's where we are.