Thank you very much. I fully understand that both options of Spiral and 2D filleted corners are important for high speed machining of the constant Z strategy, Unfortunately the spiral constant z toolpath is always in 3D and so it cannot be smoothed by 2d arcs at corners as the current code implementation. We, developers, might need to reconsider this. That is, shall we first fit all constant z segments by arcs in 2d and create the spiral toolpath from the arc-fitted segments? Some more feedback and testing are still required before changing the code.

I opened the development/bug task https://jira.autodesk.com/browse/PMILL-19963 for Powermill developers to have a further look. Thanks.
