Nothing can be cut here.
Can only be defended.
That's not the point... Sabo loses a good factor of his offense, a good part of what makes him that powerful while Zoro doesnt. From the get go, you can tell Sabo is at a disadvantage here.
Sabo is not at a disadvantage though
His haki, physicals, and CQC skills are unaffected
Zoro doesn’t have natural durability or resistance against fire
It is a matter of CQC and who lands more attacks on the other, maybe one attack but that’s besides the point
Zoro countering mera AoE is not a nerf to Sabo
An example of a real disadvantage is Kizaru vs Akainu, Kizaru would have a seriously hard time dealing heat based damage to someone on his level that is heat resistant