Makes sense especially the BM part. I've been thinking her durability haki related since the photo shit. But we will see. Problem is wit oda, no telling when that'll be smh...
so we assumed her body is naturally tough
btu then this happened.
and she bled from her knee so its clearly something she has on when she's conscious (prob haki).
common thing here , hardness, no scratches , no nicks. another thing , while coa is finite, this hardness doesnt seem to be limited to the user's haki.
we also know luffy and kat channel adv coo differently (luffy through emotions). its not farfetched. special credits to @Rosella.Fiamingo .