The Boolean operation result does not meet expectations.

[PPDEMOone]

Description/Steps to reproduce

I want to get the result of the union of two SVG paths.

paper.setup(new paper.Size(1, 1));

const up = new paper.Path(pathString);

const down = new paper.Path(pathString);

paper.project.activeLayer.addChild(down);
paper.project.activeLayer.addChild(up);

const svg = down.unite(up, {
  insert: true,
});

console.log(svg.pathData);

I got this

I'm not very clear on the rules for merging, even for intersect and subtract.

Link to reproduction test-case

https://stackblitz.com/~/github.com/PPDEMOone/paper-boolean-operation-testing-snippet?file=index.ts

Expected result

Additional information