Degenerate triangles on boundary

I've been chasing an unexpected behavior and boiled it down to a very basic input. I'm adding points to an existing triangle (on boundary, inside, etc) and using Delaunator to retriangulate and Constrainautor to constrain certain edges. I've been getting degenerate triangles on the boundary.

Consider this input:

[[0, 0], [30.51591076416662, -5.272057753973058], [13.955446995823877, 16.74653639495955], [22.3355613751919, -3.8587860099360114]]

The first three points are the original triangle, and the last point is one I add, which was inserted on the edge [P0, P1]. Delaunator treats the 4th point as inside, instead of on the convex hull.

I get the following triangles:

[2, 3, 0], [3, 1, 0], [2, 1, 3]

And the hull:

[2, 1, 0]

A visual of the data, where the blue line is the degenerate triangle (note, I'm in a +Y up coordinate system, so everything's CW) -

Start by reproducing the reported result with the four-point input using Delaunator, then inspect how it classifies the fourth point and constructs the hull and triangles. Done means the boundary point no longer produces the reported degenerate triangle while the triangulation and hull remain valid.