That's not exactly how the "rule" works. You're probably aware that all nouns in Russian are hard or soft, e.g. хлеб is hard, голубь is soft. Well the same is true for all adjectives. Hard adjectives will end in -ый in the masculine nominative singular form, whereas soft adjectives will end in -ий. There's a third ending -ой that is hard adjectives with a stressed ending. I've not come across any types other than those thus far. Then the suffix for hard adjectives will be hard in all cases, and soft for soft (with some exceptions).
Getting back to your question, the letters you've listed are not the only letters that can be followed by -ий. These letters cannot ever be followed by a ы. So when you have a hard adjective with a stem ending in one of those letters, and an expected suffix that starts with ы it gets changed to и. In all other cases the adjective will keep a hard suffix. But it is possible for any consonant to be followed by -ий in a soft adjective.