Fact: where a pellet lands with a springer does not have to have a direct relationship to where the barrel was pointing before the shot was let off.
Why? Because the gun starts recoiling, thus deviating from the point of aim, as soon as you pull the trigger and the piston starts to move. There is quite a lot going on before the pellet even starts to move.
So? Where the barrel ends up when the pellet actually leaves the muzzle depends on how the recoil changes the position of the gun in relation to where it was when you pulled the trigger.
Where exactly? Depends on how the gun is held. This is what hold sensitivity is about. Zero using one hold, change hold, and the barrel ends up elsewhere.
Translation? Barrel may well (and generally is) pointing off-target prior to the shot being let off. The gun then recoils, the barrel (assuming correct setup and consistent recoil management) then comes on target just as the pellet leaves the muzzle.
In your case recoil due to your particular hold means that the initial position of your barrel is off to one side a fair amount, which is why the rearsight windage adjustment is not inconsiderable.
If you are shooting consistently and you have enough adjustment available to you - no worries and well done.
**WANTED**: WEBLEY PATRIOT MUZZLE END; Any Diana/Original mod.50 parts, especially OPEN SIGHTS