Only really an issue in the headless-sse client (e.g. used in tests - acceptance tests etc) where the client is disconnecting and reconnecting (e.g. between test suites). In the normal/browser case, we don't disconnect, so we don't see it.
In fact ... is only seen in the acceptance tests when running in dev mode (--dev) and when running multiple suites at once (disconnecting and reconnecting between them). Causes the second tests to hang because they do not see the events.