You're not entirely wrong here but Advanced CoA can be used for defensively
and offensively. He needed CoA to harden his legs so he can withstand the flames better. That much is true. However, Sanji needed a better damage dealer against Queen so Advanced CoA is perfect for that. Remember, Sanji stated that his weight aka strength and speed are different levels above.
About the third level of CoA, if you look at the last Sanji panel carefully, you can see the explosions behind Queen when he got send flying by Beef Burst, and Sanji attacks him from the front, that makes me think that was level 3 CoA. "Destroys them from the inside out", Sanji basically hits through Queen's body.