Why is the horizontal spline not drawn?

Question

SVG

Guys, please help me understand why using the d3 library it is impossible to draw a spline for a set of points that have the same values ​​along the vertical axis.
Here is a working demo . Here is a non-working demo .
The only difference between them is that in the first demo, I initialized the first point with a slightly different value:

const responseData = [
  { dateUnix: 1534809600, price: 34545.01 },
  { dateUnix: 1536809600, price: 34545 },
  { dateUnix: 1538809600, price: 34545 },
  { dateUnix: 1540809600, price: 34545 },
  { dateUnix: 1542809600, price: 34545 }
];

This solved the problem, but I would like to do without such a crutch.

Answer 1

look - googled for you