Could be they already owned a Bully and sent it to him for rebuild and blueprint.
I own two Martinbuilt Touch clutches, and my first clutch by him was a bully.
Out of all three clutches there is little difference but the Touch seems to be a little more tunable without sending it back to him for specifics. The wear on the clutch seems less significant in the times between rebuilds requiring less to rebuild them. They work easier to do the same jobs. "Cheaper" in the long run as they don't wear out as fast! I will recommend any clutch to David as he's top notch. His clutches have put us in the winner circle and have never had one fail! Not to say that they can't, everyone makes mistakes and things just happen! But, he stands behind his products and anything he builds. So choose either and you WILL NOT be sorry. If you have a Bully and want the best, send it in. If you want a Touch you'll be very pleased with it!
Single disc option you'd have to call and talk to him about, that I don't know.