I don't think it can be called cash since no one is going to accept it.
Like it's so stupid, even if the other person were to accept bitcoin or whatever they'll still need to verify if the address contains crypto or not and whether the private key is valid (both of which needs internet access on some electronic device).
Lol, they reinvented certified bank drafts which are barely even used anymore since you can transfer money online so much easier and more securely.