Do you know this thread about this device:
With Posting #106 there is someone stating that there are (at least) two different versions of this device. The newer one has to be defined as SWITCH and the older one as CONTACT.
Are you sure that all of your fgk-101 have the same revision?
Regarding sensor_binary (and that’s only a wild guess from me): Sensor binary is the gerneral class of the whole device. The channels of this device can of course be other classes. Your item definition looks good to me (as long as this revision is the old revision using the CONTACT type).