The A20 VI has no independant backworking tools. Your backwork is done with tools mounted in an endworking type station with the tool facing the subspindle. This works very well as long as your part cycle allows this without adding cycle time.
The A20 VII does have 4 backworking tools mounted separate from the Gangblock thereby allowing you more freedom. You still have the added ability of using the gangmounted tool positions to work on the sub spindle. That would give you 8 possible positions for backwork, 4 independant and 4 shared.
Either machine is a very well made and easy to learn machine.