I think the point is that he shouldn't be used for breeding AT ALL.
If I recall correctly, a single comb is a recessive trait, which means he is homozygous for single comb and will pass it to all of his offspring. If the other parent is heterozygous for the walnut comb, half the offspring will have a straight comb (assuming Mendelian genetics, which isn't guaranteed in the real world) and it will take 3-4 generations to get a single bird that is homozygous for walnut comb.
If you really are going to breed silkies, it will be easiest to save yourself the plethora of poor quality offspring and not breed him. You have a second roo, right? Your best bet is to sell the straight comb one as a pet and use the other for breeding.