Can you elaborate or explain the concern more succinctly?

If you are simply referring to someone (not the mint) being able to double spend ecash tokens while there is some internet outage, then yes this is possible. However this does not inflate the supply, because when the internet is restored, the token needs to be refreshed and it is first connected, first serve. The rest will stop trusting this customer.

Of course you can choose only to receive offline ecash from people you trust, and keep in mind that no other custodial solution is able to offer offline payments, but if they did, they would have similar issues.