To compare to other frameworks out there:
featherjs: A framework for real-time applications and REST APIs
meteor: THE FASTEST WAY TO BUILD JAVASCRIPT APPS
deepstream: a fast and secure data-sync realtime server for mobile, web & iot
The problem is that once you provide more functionality then pub/sub you end up in this vague toolkit statement land.
I would assume that the issue is more around the fact that the term data synchronization is still not used as often and so doesn't give the same familiar feeling people get when looking at other pub/sub frameworks. Deepstream supports HTTP/MQTT/Binary and JSON websocket protocols for rpcs, records, events and presence. Maybe that should be the sentence!
A secure scalable realtime server that supports HTTP, MQTT and WebSockets for rpcs, data-sync, pubsub and presence functionality