Message-routed deliveries (for the same priority) are forwarded over the same inter-router link when moving from router to router. If a streaming delivery is flowing over such a link, subsequent deliveries on that link will be delayed until the streaming delivery is complete. A solution is needed that allows an arbitrary number of streaming deliveries to concurrently flow from router to router.
DISPATCH-1765 means the feature added here will not activate between a 1.14.0+ router and earlier 1.13.0 routers. This is why 1.14.0 followed so quickly, and it should be used in preference to 1.13.0 as result.