After seeing that Kaido Meow had more or less mastered his Devil Fruit Ability, Xie Wen and several of the combat-oriented cats sparred with him on the island.
This was both to get a clearer picture of his current strength and to help him grow familiar with his two newly acquired powers, Haki and his Devil Fruit Ability, more quickly.
Although Kaido Meow might have had the greatest combat talent of all the cats, and his unusual size went a long way toward making up for the Palicoes' innate lack of strength, he had only just arrived in the One Piece world. Never mind comparing him to the original Kaido-without using his Devil Fruit Ability, he did not even have any particularly good way of dealing with Jinx Meow.
Even after using his ability to transform into his strongest half-dragon, half-cat beast form, Kaido Meow still could not handle Meow Jūshirō and the others...
Having Observation Haki or not made a huge difference.
Still, whether it was because he had eaten the Sakura Dragon Fruit or because Kaido Meow naturally possessed formidable defenses like his namesake, while his lack of Observation Haki left him unable to deal with Meow Jūshirō and the others, they likewise could not break through the defenses of Kaido Meow, who had already learned Armament Haki and was improving rapidly.
Of course, if Meow Jūshirō and the others used powerful moves such as Heavenly Soaring Cat Flash, they would certainly be able to hurt Kaido Meow, but they were only sparring, so naturally they would not use anything too dangerous.
The reverse was also true. If Kaido Meow unleashed AOE attacks in his Sakura Dragon Form, even with Observation Haki, Meow Jūshirō and the others would have a hard time dodging every attack.
Also...
That little