They are not sats, mints do not need to be backed by sats in order for the mint operator to send some one ecash, nuts or whatever units the mint is issuing. Technically the ecash tokens are in a separate system that is not dependent on Bitcoin at all. Ecash can be generated within a mint that has 0 sats backing it. That mint just wouldn’t be interoperable with other mints and or lightning.
Discussion
yeah, proof of assets is a big deal in all such certificate issuance businesses
it's the thing about bitcoin and lightning, they are sats... everything else is bullshit