Cats and kittens are the masters to adapt to circumstances. They have flexible body, but their mind is flexible as well. Cats are very smart from babyhood and if they need to get inside they will find the way.
This little kitten also found the solution – rather unexpected, I would admit. Less clever pet would meow for hours near the door, but this kitty does not face any problems when the solution is so evident.
If cat has claws and can climb anywhere, why not use these abilities? Still I would advise the owners to find safer method to enter home for the kitty. I still admire kitten’s quick wit and creativity.