I encountered this in my most recent GAC battle. They only put the Executor for defense, leaving every other defensive slot open.
If you do a standard defense and save some units for attack, they have all of their best units and counters to take out all your defenses.
While you get max points for all of their unfilled slots, they will still come out on top after clearing all territories.
After scoping out my opponent on swgoh.gg, my gut told me to put all my best units on defense. But I second guessed myself, put in a standard defense, and lost.
It is a despicable tactic of someone utterly incapable of winning a straight up match. If this becomes a standard tactic, it will entirely ruin GAC.
(Edited to correct autocorrect typo)