I've always understood it as Luffy having Basic CoC, while Zoro having Basic CoA better than other Two, and Sanji having better Basic CoO.
You need to understand that those SBS questions weren't necessarily sent around the time Oda answered them, and each question was probably one among countless similar ones,
Oda deciding to answer that question at the time, means He wants you to only understand it based on what you know from the Manga so far, you think He wasn't asked when Story was still in Fish-Men Island? How can He do so when Zoro & Sanji weren't confirmed to have Armament Haki yet in Manga at the time?
They were confirmed to have CoO in Fish-Men Island, but it was until second half of Punk Hazard Arc that Zoro & Sanji were confirmed as CoA Users, so Oda finally decided to answer that question in SBS of Volume 71 (Start of Dressrosa Arc), where Readers had only Basic Three Haki to compare,
Stop using SBS out of context, those Answers only use what We know at the time.
That particular answer was only for their Basic Haki Mastery coming out of Time-Skip, it's not their Lifelong Specialty.