うverbs finish with る

For verbs ending in 「る」, if the vowel sound preceding the 「る」 is an /a/, /u/ or /o/ vowel sound,it will always be an u-verb. Otherwise, if the preceding sound is an /i/ or /e/ vowel sound, it will be a ru-verb in most cases.

It is said that but it doesn't follow the rule above at all because the following is うverbs finished with る

the うverbs that doesn't follow the rules above
かえる　e
はしる    i
つかれる e

The うverbs that follow the rules above
サボる　o               
とる　o
のぼるo