Question regarding GMY bonus turn from Masterstroke

It is pure RNG if both are 100% TM. It works just like Home One’s ultimate buff. If an enemy ship hits 100% TM during your fleet’s bonus turns from the buff, the opposing ship can go first. If it’s a mirror match and the enemy Ackbar gets to pop off their ultimate right after you apply it to your fleet, the enemy team can destroy your fleet or rob your TM due to RNG. GMY is same concept.