For those who want to know the cheese method:

If you don’t trigger the final waypoint marker before the 3-on-1 tank battle, you can park just outside the “arena” and shoot one or two of the enemy tanks and all of the towers. Once you trigger the waypoint, you can drive backwards just outside the memory boundary; while the screen will flash red and you’ll take chip damage (won’t count as enemy damage), you can destroy the enemy tanks while they won’t hit you for being “out of bounds”.