Moment of Clarity – Gain an attack of opportunity for you and your pet on interrupting a foe. Daze and stun durations you inflict last longer. Interrupts caused by your pet do not trigger the effect. http://wiki.guildwars2.com/wiki/Moment_of_Clarit
Pet is part of the ranger, i think when pet interrupted, that should proc Moment of Clarity
There are some couple reasons behind this
1. Not all pets have CC skill, only Drakes and Canines do
2. The player doesn’t have control over the CC skill
3. Pets don’t always land their attack