The following tasks mention problems with the fill / erase tool and they all boil down to the same issue:
Currently the fill / erase tool works in a way that everything, that is encompassed by the imaginary area the user clicked on, is filled / erased
- that's the reason why "B" is also filled in the task description of T28145: SetRegionTool does not work as expected (flood fill like) with concentric structures.
- that's the reason for the two different results in the images in T28763#229381
- that's the reason for the user feedback in the task description of T29078: [Segmentation] Erase tool has unclear edge cases (see also @kislinsk comment T29078#236006, Example 1)
We have to make a decision how we expect the fill / erase tool to behave and act accordingly.