While some S0 devices have a way to suppress secure inclusion many do not.
The C-5 has an option to disable S0 for everything except locks and garage doors.
The C-7 does not have such an option. If the device supports S2, you can disable secure inclusion by unchecking the boxes when prompted, but the prompt does not appear if the device only supports S0. I would like to request that the C-7 present the prompt even if the device supports only S0.
I am speculating a bit, and going by what I remember in a couple other threads.
If I understand correctly, this is part of the Zwave specs, and the C7 is doing the right thing. The C5 may not have been following the standard exactly? Or the standard is different between generations?
There are a couple posts about this elsewhere on here, but I didn't dig for them. One of the Hubitat team explained it before.