I was confused by this too because there is already an On/Off matrix and yet many people had threads as opposed to the matrix.
The matrix is good at a glance to get an idea of what people are into (and conversely, what their boundaries are.) but I think it's main purpose is to make your interests searchable. The Find Partners uses the matrix as a database to find like-minded people. A more detailed On/Off page seems to function as giving yourself a platform to be more specific about your needs.
I would look at what other people have for their On/Off threads and use them as an inspiration.