It's because the arena is pushed into true blue 1945, and the increased realism in the gunnery department made speed an incredibly important asset to the fighters.
In AH1, you could hit and kill at longer ranges up to about 500 yards easily. Better experienced pilots can intentionally hit things at 600~700 yards with .50s or Hispanos, and underexperienced pilots can also expect a kill with a bit of luck. And if one gets really really lucky, he would be able to kill something at 800~1000 yards with freak shots.
Now what this meant, was when the E states are about even, no one can really run away - if a chaser was inside 1000 yards, people had to start considering whether they should initiate a break turn, admit that they've failed in running away, and have to engage.
Usually around 700~800 yards the chaser would lob a few rounds as a threat, and the chased one would turn around and start evasives.
....
Now in AH2, most people can't hit shi* outside the 400 mark. Having to close in an extra 600~700 yards than it used to be in AH1, into a plane like the P-51D or the D-9 or the La-7, can easily take some extra 1~2 minutes longer. It takes longer time to get into range when the enemy decides to run, and very slight jinks are enough to evade most attacks upto 400 yards.
So, what happens in those extra 1~2 minutes? Planes like P-51 or the Fw190D-9, La-7, with deck speed pushing over 360mph, can cover at least 6~12 more miles in distance.
So, what happens if they can run away 6~12 more miles? They meet help, or a friendly base(assuming two hostile planes met somewhere in the middle of two hostile bases).