Inaccuracy when creating an extrusion from planar curve

There is no imprecision. That is a very small number, several orders of magnitude smaller than your document tolerance most likely. The number is essentially the same as 0.

Points are always going to be floating point numbers. This forum is full with posts on floating point accuracy, for instance 0 ≠ 0 ...can someone explain? as one fairly recent topic - don’t forget to read also the linked topics further down the thread.