It seems that the function applies its rule to all input words, regardless of their type or category. However, it is possible that certain input words may not produce the expected output, depending on how the function handles certain special cases or edge cases.

[DESCRIPTION]: The function applies a simple substitution rule to each input word, replacing each letter with the letter two positions ahead of it in the alphabet. This rule applies to all input words, regardless of their type or category. However, the function may not handle certain special cases or edge cases correctly.