It was worse than worse. Follow up answer to this guy explains
If I am able to break your leg bone almost in two from an ankle clash where you put up a decent check high up on the knee joint, it means if I can break you like that wihtout actually leveraging any hardness in the hit, any other clashes where I use my shin with the same power, I should be able to break you a lot more. Sanji's fibula almost tore in half, mf
Are you a retard not to understand this?
It means Vergo was half assing the whole fight and putting in any power in his clashes save for this one actual clash that Oda highlights as that is the only instance where Sanji actually experiences a significant break yet Vergo leverages no hardness in the hit. We can conclude from this that the rest of the fight was Vergo just toying and not putting in any effort or power, or Sanji would have been a literal pile of bone if a simple ankle kick had the power to do that.
Vergo was toying with the dude. Sanji could barely even dodge a playful roundhouse swipe from Vergo when Vergo could have just kicked Sanji in instead of trying to fancy shit. Vergo was just having fun and Sanji was a fucking pissbug in every sense to him
Vergo could have ended Sanji with just one serious kick. The only actual instance of him being serious was the fucking ankle kick, and that fucked up Sanji worse than anything in his life