You're correct. The 8.2 was used in Buick, Olds and Pontiac. The Chevy 8.2 "10 bolt" is not the same. It uses "C-locks" to hold the axles in. The BOP is a "semi-floating" axle, with the bearing pressed directly on the axle, held in place by a flange and bolts.
The 8.5, on the other hand, is the first true "corporate" rear, as you suggest. Loosley speaking, the 8.5 is a redone version of the venerable Chevy 12-bolt, with only 10 holes drilled in it. BTW, the terms "10-bolt" and "12 bolt" refer to the number of bolts that hold the rign gear to the carrier. There's the common misconception its number of bolts holding the cover on. While, for the most part, that's true, not always. The '70 Olds and Pontiac "performance" rear (in W-30 and Ram Air cars) had 12 bolts holding the cover on, but 10 on the ring.
The BOP 8.2 is actually a very good rear. Tough stuff. In the F-body (Firebird), it's been used in cars going deep into the 10s and not yielding a bit. In the A-body (GTO), traction is a bit "better", so the rear isn't quite as tough. Fine for anything under 500 HP and not drag racing with big slicks.
Jim