Yes, commonly called the butterfly bush. many unusual plants can and have been used for bonsai including grape vines, rose bushes, lilacs, jasmine, thyme, blueberries, etc.
http://www.bonsaiboy.com/catalog/flowering.html
The point was larry, bonsai is defined as a plant in a tray.
This definition precedes you by many years. Grafting many seedlings together doesn't disqualify a plant from being a bonsai any more than grafting a branch on does.
You said that you wouldn't call this bonsai, I respect that opinion, however it is a wrong opinion.
Now
these are not bonsai....
Will