Aren't bushed and BB engines often the same, crank-case-wize? I know that some aren't but I think in some cases the shell is the same, only bronze or similar cheaper-than-ball-bearing bushing is substituted in the spot where the bearing goes..
Those ap guys might not have bothered to make two different engine cases for the wasp, with the exense of the dies etc..
I guess maybe looking at a parts blowup would tell.. Image swiped from hobbypeople...sorry.