Yes because Sanji dwarfs Zoro
That's what you morbid delusional ones wishfully dream
While
Yes because Zoro dwarfs Sanji
That's what Oda thinks
Therefore all this
The occurrence that the author chose to have Luffy and Zoro share so many main traits, while he didn't have Sanji share them with the Captain and the Number Two/Right Hand Man/First Mate, is a factual evidence. It definitely makes you think that Oda was trying to portray something...
I mean, Sanji literally viewed Zoro and Luffy as both inspirational figures to take example from.
So it's not surprising that this was the strength ranking of the Monster Trio.
That's why Zoro got this portrayal of his strength compared to Luffy's.
Something that Sanji never ever got.
That's why this happened between Luffy and Zoro.
While, in spite of all the gags, it never happened between Zoro and Sanji.
That's why the maybe greatest and most iconic power of the manga (the will is one of the focal point of this series and Conqueror Haki is literally the power of the ones with the greatest will), the one hyped by Kaido as the gimmick of the top tiers ("only a handful of the strongest can") was given by Oda to only Luffy and Zoro. Zoro even unlocked that in the same arc of Luffy, just a few chapters after him.
No wonder that Oda officially stated that Zoro is the number two in strength in the Strawhat crew. Meaning that it is undesputable that Zoro is a good deal stronger than Sanji (just like Rayleigh than Gaban, King than Queen and so on). Which was common sense for most, but anyway, I am glad that Oda cleared this once and for all, even for the most biased ones.
The author didn't pick Queen, Sanjj, Gaban, Jozu and so on. He also didn't pick King + Queen, Zoro + Sanji, Rayleigh + Gaban, Marco + Jozu and so on. No, no bullshit of that kind. Oda picked King and King alone, Zoro and Zoro alone, Rayleigh and Rayleigh alone, Marco and Marco alone and so on. And he stated that the ones that he picked were there because they were the number twos, explaining (with the Bepo vs Penguin/Shachi thing) that he means the second strongest in the crews and groups.
Sanji is strong, indeed. He is just not as strong as Luffy and Zoro. And that's the reason for why Oda reserved a similar portrayal for the latters, who share many parallels and comparisons in strength, power ups, backgrounds, paths, benchmarks and goals.
Also I'm not arguing that Zoro is exactly pound for pound as strong as Luffy. He definitely is not. But is close enough to be extremely comparable. This at least before Gear 5/Nika Nika thing.
I mean, it's a fact that Oda had Zoro share all these parallels with Luffy. While he didn't have Sanji share traits with Luffy. That's undesputable.
Like it or not, the amount of different times and different ways where Zoro is put close to Luffy is gargantuan. The sheer number of those comparisons is astonishing, it screams loud, like the absolute absence of the same closeness between Sanji and Luffy, screams loud as well, but in the opposite way. Even the most biased Sanji fan has to at least admit that...
Luffy > Zoro >> Sanji >>> other Strawhats
Luffy is a tier above Zoro. Zoro is two tiers above Sanji.
Luffy is a solid full fledged Top Tier.
Zoro is a Borderline Top Tier, stronger than YC1s but still not as strong as a full fledged Top Tier.
Sanji is stronger than YCs, but still weaker than YC1s.
