No it is, Sanji currently doesn't have feats to show even with Raid Suit he can give Zoro anything more than a low difficulty fight. That is not a wild take, the discrepancy in their feats, portrayal, hype and presentation is legitimately that big.
Okay so if the biggest head that Zoro takes down is stronger than biggest bet that Sanji takes down.
So these are conditions of the bet but winning prize is still not fair, its like if you win, I give you $10,000 while if I win, I get $10. Most of the Sanji fans believe Zoro is stronger than Sanji, even if by slightest while I am arguing for a hot take.
Plus Zoro < Sanji is a way more daunting task to argue, than Zoro > Sanji where Oda is doing 99.999999% of work for you.
Its not about what you personally feel, if I am arguing a hot take you have to argue a hot take as well, so I will argue "Sanji > Zoro" only if you argue "Swordless Zoro > Sanji".