As the author puts it [0], the issue is that if you expand or contract an ellipse by a fixed radius in every direction (e.g., if you create inner and outer walls for an elliptical corridor of constant width), then the resulting curve is no longer an ellipse. In contrast, piecewise-circular arcs can be expanded or contracted and remain piecewise-circular, though the control points will shift around as you transform it.

[0] https://medium.com/@brunopostle/hey-ovals-are-better-than-el...

If you want the resulting geometry to be precise you are pretty much limited to equivalent of compass and straightedge (or well, in mechanical engineering lathe and mill, which are basically the same things). if you start somehow calculating the geometry you are limited by precision of the calculation, but more importantly by precision of measuring distances you can achieve.