Just forget about that … Blynk seems to use BT/BLE differently, basically as a simple link.
It should work as well… but there are some more things to consider with Blynk and BT/BLE… they are effectively still in beta it seems, and possibly lower priority in development then normal IoT networking methods like WiFi.
You need to have the latest BETA version of the App… I think they are still running… With Android, you scroll to the bottom of the Blynk Play Store page on your phone and somewhere you will see option to join Beta program.
With iOS, follow this link - iOS 2.26.0 BETA available