The factory made thousands of BB cars with both seals, very few leaked
The rope seals are harder to install properly so they don't leak and they need the knurling to help wipe the oil off the seal
If your crank is smooth or worn down on the knurling use the newer Viton rubber seals and use a adhesive type silicone sealer to seal the two ends together and to seal up the side seals to the seal holder