You're missing the point here,
Sanji before would have loved to have CoC, but now that He heard Zoro has it, He "Needs" CoC,
Now, Sanji is in "I need to Power Up" Mood,
If Gaban told him: "Yes, you have CoC", then Sanji have nothing to worry about,
He got his Confirmation same as Zoro, & if He shows it in their Next Fight, it won't surprise Zoro cuz He also didn't know He had CoC,
Now, i'm not saying Oda can't give Sanji CoC, that's obviously the easiest Scenario He could go for here,
But it's also highly possible that Gaban's Words were only to make Sanji wrap his head around finding something that Compensates for his lack of CoC (Regardless if He ever gonna have it or not later on),
If CoC really Counters everything, then only another CoC can oppose it, so how can Sanji answer himself on how to compete with Zoro?
Thankfully Sanji is not a DF User or a Lunarian or Cyborg ... etc He is supposed to Surpass all kinds of Defenses, so this Scene should be his Motivation to come up with something that can handle CoC outside Haki (Just like Kizaru/Vega couldn't explain how He countered that Laser),