Having a user modify defaults is not a good solution. A user should not need to know underlying behaviour/quirkiness to have a model be precise.
IMBack showed code that works with correct radius, for other cases. Why not fix all locations to use correct radius?
To an end user, it doesn't matter what kernel FC is based upon. If there are other cases that need fixing, then fix those too.
Basing a radius on a tesselated circle's bounding box is FUNDAMENTALLY incorrect regardless of default precision. Tesselation isn't the same category as rounding error / truncation. If code is based on tesselation like this, it will fail in the future.
One might actually WORSEN the default Precision (set it to 10mm!) then use freecad to find/debug all the bad occurrences of using a tessellated circle's radius.