The regular Lee Classic O press the threaded portion for the die is a bushing. Threaded on the outside to screw into press, inside to match dies. The Hornady locking die collars that are the Breech Lock equivalent use a bushing with the same outside threads as the Lee press has.
In short one can unscrew the steel die bushing from a regular Lee O press and screw in the Hornady bushing sleeve. The reason I mention this is I wonder if the Breech Lock challenger sleeve is screwed into the same threads as the classic O press. Manufacturing process would be simpler which makes me think that maybe the difference between a Lee Breech Lock and Lee Classic Cast O press is which bushing gets screwed in. One threaded for dies or one with twist lock for the Breech Lock version.
If the two die seating bushings are able to be swapped that would potentially allow one to use the regular threaded bushing in this new press. Avoiding the cost of twist lock collars for dies. I use a turret press and store my dies installed in a turret disk so my dies remain set up. Have done some research on adding the Lee Classic cast and possibly using the Hornady quick release system. I like the solid nature of fully threaded dies. The convenience of twist lock could be useful. So having both as an option appeals to me.
Whomever gets one it would be interesting to find out if the breach lock sleeve unscrews and a regular Lee press die bushing fits in it's place.