Correct; it saves snippets in the App's preferences plist file. The version in
~/Library/Containers/Whisk/Data/Library/Preferences/com.tumult.Whisk.plist is the canonical location used by Whisk. If you hand-modify this, you will need to run
killall cfprefsd afterwards in the Terminal for the changes to take effect.
The version in the
~/Library/Group Containers/8J356DM772.com.tumult.hype.shared folder is just a copy. It is only currently written to and not read from. It is basically just a safeguard for us (the developers) in case Apple adds some sandboxing restrictions in future versions that would restrict us from doing old version migrations.