Operating system: Linux-5.11.16-2-MANJARO-x86_64-with-glibc2.33 64 Bits
Graphics card: Mesa DRI Intel(R) HD Graphics 4600 (HSW GT2) Intel Open Source Technology Center 4.5 (Core Profile) Mesa 21.0.3
Broken: version: 2.93.0 Beta, branch: master, commit date: 2021-04-23 20:24, hash: rBaa95f8019e42
Worked: (newest version of Blender that worked as expected)
Short description of error
Operation which creation of circles such as Add->Mesh->Circle, Add->Mesh->Cylinder after applying have asymmetric position of vertices, which can give unexpected results such as Boolean operation with the selected Exact method.
I created two circles - A and B. Circle A was created from menu Add->Mesh->Circle with radius equals 50 mm. You can see on image that parallel vertices top and bottom has asymmetric position. Also, the asymmetric arrangement of the vertices gives different lengths between the parallel vertices, which indicates that the circle has non-symmetrical edges. It shown on next image.
Additionally, for comparison I created second circle B from one quarter of circle and mirrored by X and Y axes for symmetric. Circle B has symmetric position of vertices and also symmetric edges and correct radius.
This issue can affect in boolean operations with Exact option and give unexpected result when parts of meshes arrange symmetric, for example:
Also I added to the file object created from correct circle primitives and I got expected result of Boolean operation:
However, I noticed that the inaccuracy can see when use the millimeters system of measurement. If you switch to another system, asymmetric values you don't see but the issue will remain. What units use for calculates inside Blender?
Exact steps for others to reproduce the error