The rumor came through 3 Tech workers. 1 of whom owns my old 280 with the Autopower weld in cage, and one that is his crew chief.
Personally, I never considered the Autopower cage all that strong when I put it in the car in the first place in 1989.
Both the main hoop and the rear legs mount to the front of the rear inner fender which would take all the load of both in a rollover.
I've got a 240 with a bolt in cage of unknown manufacturer that has the main hoop to the floor pan, and the rear legs go to just about the same position on the inner fender.