Supercontrols do not send their own values by default. There is a global option to enable this.
[Screenshot is 1.3.8, pre-release]
Hopefully in the future, you'll be able to turn this on per MIDI connection (and/or per control), but this is not yet contemplated in 1.3.7.
For now, use with caution. In most situations users do not want their supercontrols to send out.
See the Supercontrols Reference for more on supercontrols.