Eh? It's a service. It represents a domain operation (or group of operations) that hasn't been coalesced into either a value type or a transient entity, both

Eh? It's a service. It represents a domain operation (or group of operations) that hasn't been coalesced into either a value type or a transient entity, both of which are also models without database tables, both of which are preferable to a service if they fit the domain. None of this says that putting business logic into a separate class to the thing that happens to back onto a database row is correct because of single responsibility. That's a fundamental misunderstanding of the SRP.