PoL has been "coming" for a while now, and could have been implemented many times in the last 2.5 years it was proposed. I still have yet to see an implementation of it.
The problem with all of these systems in general is that they are inefficient after a few payments per day and unnecessarily complex to implement.
For a service, custodians are very hard to trust, and using Cashu or similar schemes have a lot of potential failure paths and edge cases that can be handled. And a service running their own mint would not want to offer withdrawals.
At that point, you may as well use a credit stored in a DB. There is a reason you see disposable account numbers everywhere and ecash based systems nowhere: It is pointless and a hassle for the average user and the service.
You can always create a new account number for each payment.