That statement doesn’t make much sense. The Blynk.syncAll or Blynk.syncVirtual(VPin) commands are requests send by the device to the server to ask the server to send the current state of all or some of the virtual datastreams.
This has nothing to do with the process that you’re wanting to achieve, which appears to be having a method of signalling to your device that either the app or web console is open so your device(s) should start sending data at a higher frequency.
Have you looked at the use of data invalidation to ensure that users aren’t confused by seeing old data?
You’re more than welcome to create an “Ideas” post, or contribute your use-case scenario to one an existing topic like this one…
Pete.