Question about attack phase in GA

When does the attack phase officially end? I ask because I lost GA today and watched the guy hit my last ship node with 10 sec left in attack phase. Then it went into the tally results and he happens to finish before that was done and he won. I thought when the time for Attack phase is done that is the snapshot of the end of the battle? Why does that phase get extra time. Setting defenses does not or preview phase does not.