Unfortunately, your rings have failed to seat and they never will.  Your
rebuilder knows this too.  Take it back and make him replace the rings with
good quality rings.

This happened to me, and my rebuilder didn't hesitate to replace the rings.
Mine were even worse, a quart every 450 miles. Told me about 10% of the
piston/ring sets he gets fail to seat.  Good old aftermarket quality!

P.S., I have a break in procedure that has served me well over the years
that I learned from an old racing mechanic years ago.  Let me know if you're
interested.

Stuart MacMillan
'84 Westy w/2.1