Depends on what the SLA phrasing is - us-east-1 affinity is a requirement put forth by some customers so I would totally expect the SLA to specifically state it’s subject to us-east-1 availability. Essentially these customers are opting out of Authress’s fault-tolerant infrastructure and the SLA should be clear about that.
As TFA states, we have to offer services in that region because that's where some users are as well. However, the core of services are not in that region. I have also suggested when the time comes for offering SLAs, that there is explicit wording exempting us-east-1.