Taryn, Chimeras are in their own group because they are literally 2 plants in one with both plants being partially expressed in the pin-wheeled colored flower.

These unique plants are only stably propagated when grown from a sucker as opposed to being grown from a leaf, however, I have heard you can grow them from a flower-stalk if the stalk has large enough leaflets to allow it to survive to the point of producing plantlets (I have never been successful doing this). This also explains why they're so expensive because because the propagating expense is much greater.

This website seems to give a good technical explanation: http://chimeraav.com/growing/what-are-chimera-african-violets-a-simple-explanation/

The Violet barn has a very good explanation to your question with pictures as examples.
Type in "Propagation of chimera African violets" in their search box. They make it easy for anyone to understand by showing how it's done.