We have no reason to believe Sanji's that durable. S-Shark's attacks haven't been tested against anything for reference. The most we know is that the Seraphim's offense isn't as good as their originals yet. All other Seraphim's have offensive abilities that rival or even surpass the original Jimbe while S-Jimbe is likely still inferior to its original.
Meanwhile, we have Sanji's defense tested against Queen. And we also have the same defense being tested against shit AP bros like Katakuri. I don't even plan on being dishonest and using this in the argument because I don't think Sanji's siblings are as good as Sanji despite them sharing the same abilities.
What do you think of the comparison between S-shark and S-bear?
S-Mihawk's attack was blocked by one arm of Teach
As I said, you can't compare the characters in the previous chapter horizontally. Zoro made the king bleed, but could not hurt S-Mihawk. Zoro's attack became weak?
Sanji's brother cannot be compared with his brother because he has his own strength foundation