Major Today the body of a batch request consists of multiple statements that are either individual data request statements or data modification statements grouped within a changeset. The semantics of the changeset are that the data modification statements within the changeset are atomic; either they all succeed or all fail. A batch can contain multiple changesets.
If the batch submitter wants to submit an individual data modification statement it must be wrapped in a changeset, which adds burden on the client and on the server that must then support changesets even if they don't support multiple atomic operations.
A simplification for the client that may better reflect server functionality would be the ability to include individual data modification statements within the batch, outside of a changeset. That way clients wouldn't have to wrap individual data modification requests in a changeset, and a server that didn't support atomic sets of multiple data modification statements wouldn't support changesets.