Fair enough - aware that you're not a fan of biarcs from your thesis.

>The simplicity of the arc as primitive curve has some nice features though, for example the fact that parallel curve is nearly trivial.

Yes.

Also, IIRC, Alexey Kurnosenko uses them in one of his papers to bound the regions of when it's possible to fit a spiral to end point data,

https://arxiv.org/a/kurnosenko_a_1.html