The plist file is not used or downloaded by any of the web pages; it is only used to restore an export a .hype document via the 'Help > Restore Document from Export…' menu. In fact, this can be entirely disabled by unchecking 'Create restorable document file when exporting' in Hype's General Preferences.
We found often users would accidentally or intentionally delete their .hype document and then be up a creek without a paddle to make changes. It also helps on our end when users emailed us an export for support purposes; we wouldn't have to re-ask for a .hype document. I don't recommend removing it if not necessary, but it isn't required at all.