Yeah but not requiring a user account is not something special to ecash; it's what LNVPN is doing: pay this invoice, get this service.
(Besides, your OP reads differently. Anyway 🤷)
Discussion
The customer "logs in" to "buy ecash" and then buys the VPS anonymously (with the ecash), logged out.
Again: how is this different from LNVPN??
Customer: hits Buy
Provider: pay this invoice (could be anything:LN, Monero, eCash)
Customer: sends funds
Provider: detects funds
Provider: generates connection details & sends to customer