This operator builds a new base mesh, subdivides it, projects the detail in multiple steps and rebuilds the subdivisions. With this steps, it is possible to convert a sculpt made with the voxel remesh/dyntopo into Multires directly to work on the final surface of the model with better performance.
(edited, it usually takes about 15 - 20 seconds)
This was the original goal of adding Quadriflow to Blender. The quality and reliability of the results of the operator directly depend on the output mesh from Quadriflow. In comparison with the regular Quadriflow operator, this smooths, relaxes and projects the details multiple times in order to smooth out the singularities and improve the quality of the result when rebuilding the Multires levels.
I would like this to be as automatic as possible by default, but this could have an UI to tweak the target base mesh, face count, how much would it try to smooth the mesh and other options that may be useful to improve the result.