...the behavioral subsystem and the technological subsystem are like two different elements in a compound, not a mixture.  In a mixture, different elements keep their same properties even after they are mixed together.  But in a compound, the elements interact and transform each other, and the compound ends up with completely new properties that the individual elements didn't have.

And this is exactly the case for an information system (Figure 1): the technological subsystem transforms the behavioral subsystem, and the behavioral subsystem transforms the technological subsystem – and the result is an overall system where the behavioral subsystem and the technological subsystem are completely different from what they were before.  This is what Figure 1 describes.