If you are getting the results as an event stream, that doesn’t really save anything on client-side resources. Seems just as “real time”, just with a slightly different back-end implementation.
The difference is on the client-to-server communication, since it's a one-way stream. So you're right in saying it's just as realtime when getting results from the server, but there's added latency to each request being made from the client. My point is that this latency is probably negligible for most "realtime" applications. The benefit to all this is that you're not re-inventing protocols on top of a low-level transport, and both front- and backend becomes significantly simpler (and thus more cost effective) to implement.