I somehow missed that on his post, F3 is not the correct terminology, BC2 would be the correct one as F1 x P1= BC1 and BC1 x P1= BC2 as in second back cross to parent line.
This assumption is not accurate, if the F2 is a proven hen that lays dark olive eggs and is bred back to Maran rooster, 50% of the Pullets will lay darker Olive eggs, but that percentage is only true if you breed large numbers, say 20 hatching ess, because on small numbers, you may end up with...