There could be a few things that could be happening. Maybe you are seeing that when the Midway launches his attack, it actually splits the squadron into 2 (the planes that attacked and the planes still able to attack). Then the planes still good are able to swing around and keep striking.
The other Midway was using either the fighter consumable or you were too close to the bubble of the fighters to trigger them to attack you. Even though you fly away, they can chase you out of the circle and still do damage.
Damage is not the only way to earn XP. Spotting damage, defending, spots, all contribute to your XP (plus a win helps).