Rayleigh is a master of conqueror's haki. Him being defined as a CoA only specialist is completely made up by you.
And unlike Shanks he was never called a swordsman or swordmaster in any official media, he can fight without a weapon.
Also ssking why he can't copy sword techniques only hurts your argument, Shanks is the 2nd best swordsman alive, Rayleigh's not part of the conversation.
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Literally copying Rayleigh's shit.
"Rayleigh's epithet (\(冥王\)) translates to "Dark King," which is the Japanese word for the Greek god Hades or the Roman god Pluto, the ruler of the underworld."