"Why did you make this thread? Scales are not tougher than the rest of his body"
The constant downplay and undermining continues, even after what the OP provided. When you keep reading things that are not there, and ignore things that are, you have fully transitioned to Two Piece.
These readers see Kaido, his dragon body, partly covered in scales in only
some areas and then not in others, do they honestly think Oda just draw Kaido this way for decorations??
Same Oda that updated Page One dinosaur design, post-reveal, to keep up with new historical discovery? It matters to Oda.
He has Zoans users use abilities and powers that coincide with in-real-life qualities. Turtles have a hard exterior shell, so Pekoms attained a diamond hard tortoise shell when he transforms.
In the picture below though, we know that his tail is not diamond hard.
Kaido is an azure dragon, which is a Chinese dragon.
This is an accurate depiction of Kaido dragon physiology down to the cow ear's, plus or minus some scales.
Scabbards cut the belly, the clam-like belly, not the scales. Since dragons are known for their very tough dragon scales, common sense should tell you that you'd need more amplified power to penetrate these large scales than his smooth clam belly.