It isn't. Rather, it's a incorrectly upvoted not-so-good practice.

Why is floor function a better practice than div function?

Huh, apparently .to_i converts the first number it can find in a string

ruby returns last evaulated expression.
you will use return if you want to get out early
from a method.

You have two sums of 14 there, and although they come about with different numbers, they are not unique by the definition of the kata writer.

See explanation above

hahaha clever

Elegant use of negative index.

I personally find this really strange. I receive the same error in Ruby. While I appreciate that the final answer should be an array, I don't expect to see a Ruby error if I return an integer - just a failing test, telling me what actually was returned and what was expected.

So, is the example test case right or wrong? As I too count 4. See:

[5, 7]
[5, 9]
[6, 8]
[7, 9]

100%. 12, in this form, is not a word. I also find it odd that out of 100 test cases, only one contains a number.