Any plugin still using this API will result in the server saving an inconsistent UUID to player data files,
which then triggers warnings such as "Tried to load unrecognized recipe: bukkit:9e5b92f5-e549-4f47-b0a8-9f89390ed77b removed now."
on the players login.
Plugin authors need to define a key to keep it consistent between server restarts.
Aikar