In past whenever I tried flying over a straight road by framing it almost perfectly within the camera looking -90 downwards the drone never flies in  symytery of the road which you can see is very straight line. Even when I tried to fly a smaller section of 50 mt straight line it deviates to its right.

flight heading goes off alignmnet

My question is it a compass accuracy issue with mini 3 pro since I have done fairly accurate calibration on ground devoid of nearby magnetic feild.
Or is it that visual framing is not so perfect indicator of the drone heading, my flight logs show it flew in straight line however that line wasnt in alignment I wanted it to fly over.

Seeking help over to solve this issue.

This has nothing to do with your drone's compass.
The most likely reason is that your gimbal/camera is not pointing exactly the same direction as the drone.