I agree with you, I've just wanted to show that it doesn't have enough test cases. So it's a normal bug in the Kata:)

I did the kata before the question just was wondering why it doesn't work in that way. I've found the same problem in another kata. Please don't mind, I guess it's a minor issue with static fields out the method as you've already said.

But if you run the code in intelij, you can see that count is 11 and code works correctly with the reverese for strings.
I've added count for print.

Sorry for the confusion with static (just forgot to remove when copied from my intellij), please remove it and run it again and you will see that tests can't check the code properly.
It shows hello world expected:8 but was:11