Hi,
I can totally confirm the issue…
Old post I started 1 year ago:
I have years of experience and always could dial in (with patience 
) my printers to +/- 0,05 on 100mm via E-Steps.
The only way that works on the X1 is compensate via scaling X/Y dimensions.
My sweet spot for PLA: Scale X and Y to 100.2%
My sweet spot for ABS: Scale X and Y to 100.5%
By the way, there is also still an error in Bambu Studio in visualizing the X,Y,Z directions via the colored arrows after rotating the part depending which value you are changing (% or the the actual dimension in mm)
Object was imported and rotated 90deg in X, than:
Scaling tool and % selected → Y arrows are shown up and down
Scaling tool and mm selected → Y arrows are shown front and back
Similar issues with X and Z arrows.