It’s not just because of the sweat, as people love pointing out that Zoro has seen Mihawk sweating
It’s also not because S-Hawk showed emotions since Zoro has seen Mihawk show all the range of emotions.
Zoro says he needed to “get a better look” but that can just be a euphemism for Clashing. It’s not necessarily about Zoro having to see the “humanity” itself.
If it’s to do with the clash then is it just a power scaling thing? Characters regularly consider very strong characters “inhuman monsters.” But why is this one clash able to tell Zoro that S-Hawk is human compared to the “inhuman monster” that is Mihawk.
Seriously if Zoro is saying S-hawk is so weak, why did he fail to put him down with Kaku as back up for the entire night? Zoro and friends fought the Seraphims for seemingly 12 hours. How is a person Zoro can’t put down for hours still considered “human” compared to Mihawk?
Maybe it’s just a haki thing? Since the Seraphims being hard to put down is entirely just their Cyborg bodies and Lunarian DNA, so Zoro isn’t power scaling those things, he’s comparing S-Hawk’s haki I guess? But then this is stupid since S-hawk is kid Mihawk so Zoro is just saying Kid Mihawk has much weaker Haki then adult Mihawk. Which is obvious.
and Zoro doesn’t need to clash with someone to Haki power scale them. No one else is shown requiring to first attack people to sense their haki with CoO.
Or maybe this is just a nonsense line that doesn’t mean anything which is a thing Oda does a lot.