Not really, someone can have a COC PU without being specialized in it. Ray and Roger both had CoC but Roger was likely the top dog and the best willpower wise in the crew.
So even if Zoro has COC and a COc PU Luffy can still (and is) superior in that area.
This isn't about Specializing, we don't care about Secondary Characters, we are talking about Main Shonen Characters here.
Shonen Power isn't about Willpower, you're acting ignorant on purpose, it's about Willpower + Emotions too
U just don't want to admit it & wanna ignore the Emotions part which Sanji represents
Brook said: "Sanji's Kindness have No Limits"
And Sanji said: "My Heart burns hotter than any Sun"
His Mother literally sacrificed herself so that Sanji kept his Emotions which will prove Judge wrong by making Sanji Superior than any Cold Machine made (Such as Vinsmoke Siblings & Kuma & maybe SSG)
Haven't you read Judge's Last Speech about Sanji? Which Luffy described as Sanji's Best Treats
Sanji is the Guy who have Bottomless Kindness & Zoro is the Guy who have Bottomless Willpower, not even Death can conquer him
Luffy is combination of both dude
It's ironic that u mentioned Joy Boy who is literally named after the Emotion "Joy" !!
And when i tell u Luffy is Special because he have both Emotional Power & Will Power, you tell me No, Luffy is Special only because of his Will Power, just so that you undervalue Zoro's Power
It's so clear that Sanji's Greatness comes from his Emotions, Zoro's Greatness comes from his Willpower
And Luffy is Superior than Both because he have both those Qualities
Your problem is that you deny Emotions being a Source of Power in a Shonen, which makes me doubt how you're a Sanji Fan tbh
If u call CoC Users as Gods & they represent Power, then Emotions represents Humanity & Bonding
Luffy is Greatest King because he combines that Power with that Human Bond like no one else
Zoro is Strongest of Godly Warriors & Sanji is Best of Humans (Even Readers are starting to call him as Best Character Oda made when it comes to Character Development solely due to his Emotional Value)
Go read Gan Fall's Explanation of what True God means in Skypiea Arc
Enel was Strongest but when those Skypieans prayed for God to save them, it was Luffy who stopped Enel's Bomb
Luffy is King among Kings & God among Gods, because he Perfectly matches Gan Fall's Words & he have both Power to Rule everyone & Emotions to bond with anyone.
Stop thinking from Power Levels point of view, it will make u start to see the true Themes hidden inside One Piece Story.
Shonen MC is "Unique", he doesn't Specialize in something that others have, he is Beyond that