Artillery gets accurate if it hits something

I have made a demonstration that show that artillery gets accurate if it hits something. Is it because it gets accurucy increased from experience or is it something else?

I start firing at the newly built german HQ at 4:00.
After it hitted the german HQ its gets accurate, get a fire rate increase and it get 0.18 experience. It losses the experience after the HQ is destroyed but it is still accurate.(It losses the accurucy if I change target, not shown in this game)

Then I target the partisans I spread out. Its the same there. The artillery is very accurate. The third artillery that is hitting the ground without anything nearby is innaccurate when I dont have LoS on the ground it fires on. It get accurate when I have LoS on the ground but when I again don’t have LoS on the ground it gets innaccurate again.