I would ask Brian or one of the builders, but I am not aware of that. I just think the "early" jugs were desired for performance with any mm piston. The piston is the same diameter, so I don't know why that would be, but there may be different ports in the piston, etc, that I am not aware of. Hopefully, one of them will chime in.
If you get a good running 044/440 it should run very close to that 7900, and when you get that 064 back from Randy it should be a beast. There was a non-ported one at GTG on Sunday, and it was strong!