I am not sure if I am missing something here, but unless you have been pushed back heavily or pushed the enemy, units generally stand in the middle of the map. So it should not matter that much if you attack from the front or the back, or what am I not getting here? Why is this more special for 3v3/4v4 than for small modes? Large modes generally have more delay on plane based attacks, I just don't get why the direction is that important if units are fighting in the middle of the map anyway. If you could elaborate on that, that would be good.
No problem, I will explain with the aid of a real game situation. As I played on steppes there was a fight about the island at the bottom with fuel and VP. Germans were playing on left side. A damaged Panther that just dived in and destroyed the SU-85 that was shooting at it tried moving backwards up to base. Its motor got damaged at the fight, it was still at the island driving backwards in sight of a soviet infantry unit. Since it was real close to the lower edges I could strafe over its full length from the right bottom. The opponent tried to evade but just couldn't move out of the way fast enough. It was very close, he nearly made it. With the plane approaching from the other side I do think he should have saved his Panther.
You are surely not fighting only at the centre of the map and tanks are not always aligned parallel to the edges of a map. There are always flanks to protect and VPs close to the edges of a map. The fighting takes place there too and such situations are not rare, they happen all the time.
You won't have this problem at 1vs1 maps, they are just to small too make a real difference in approaching paths.