The client-side of a remote context might need to perform many small sequential updates (add or set requests). The batch update enables the client side of the CHA context to submit these updates as a single request.
Without the batch update, the client needs to send each one of these updates individually to the server side of the context. Each update incurs a certain amount of network and EJB latency as a part of its processing. This slows the client as it must wait for each small update to process before continuing on to the next one.