Yeah, he never once used a sword technique in the same way Shanks never once used a sword technique. The rest of that is just semantics and your head canon trying to draw conclusions from it.
Roger and Shanks are exactly like King. They don't ever use sword techniques. All I see is picking and choosing based on your wrong head canon here. The distinction your trying to make here (named attacks=difference) is your head canon. Devine Departure is the exact same as extra large imperial flaming wings as far as I'm concerned.
Anyways, I agree with this:
Shanks and Roger are just as much swordsmen as King. IN other words not at all.
Until I see the panel of Shanks/Roger saying their swordsmen that fall under Mihawks title, they ain't. They can use as many sword techniques as they want, it won't matter because Big Mom has dozens of sword techniques and still isn't a swordsman. Therefore Shanks/Roger ain't either.