This trick does not work because you can't go back to old snapchat and you are stuck with the new update!
It worked at the time of testing today, and I'll test it later and check that it's not working anymore. I did note that Snapchat was aware of this and admitted it was a temporary hack that wouldn't last forever.
This did not work and it's what I thought it was going to happen. It simply makes no sense because once you've downloaded the update, then that's what's on your phone regardless of you turning the auto update off or not. The only thing this "trick" did was to delete and reinstall the exact same thing.