Wouldn't be surprised to see differences between Win7 and Win10 - the "current working directory" concept has essentially been deprecated in Windows for a while (at least through the GUI).

Registering a system file association is something we could do for the launcher, but that'd be about it. I'm not sure it'd gain that much. Would be very interesting to collect data on who double clicks .py files vs. running them from another program or a console.