Why can't arty platoon together?

KRZYBooP: The change to not let Arty platoon happened in update 9.18 with the introduction of the Arty stun mechanic. The Idea of being able to coordinate the stun to permanently lock down a tank is the biggest reason why the rule exists and why during another update the stun mechanic gave dimensioning returns for hitting a tank already stunned. Source info HERE