From the perspective of the icon, I think it has a similar principle to the “continuous selection tool”. Is it feasible to make a “similar color selection” scheme (or an independent tool)? In the initial color matching stage, this helps to change the color at one time. Nowadays, people usually use selection and filter.
I think this option can be used as an enclosing method of “enclose and fill tool”. Generally speaking, there are things like balloons, birds or flowers in a single layer that need to be filled. If you can click once to automatically determine the closed area in the layer, it will be more convenient.If there is no selection, it should be equivalent to pulling the entire canvas with a rectangle.