Rear bump stops -- optional or necessary?

[89Vette]

All you have to do is look at the cut-away drawings on the VX JDM brochure to see that the spring helper basically rides on the rear axel to know it had to be an active part of the suspension that was intended curbed body roll.

Is there an online link? In the "Rear Suspension" diagram of this link we don't even see the stops pictured. That tells me they're not considered an active part of the suspension.