ArcGIS Pro should have the option to use absolute path names. In ArcMap, we can choose between absolute and relative. We should have that same choice in Pro.
A key reason to allow absolute path names is to facilitate a use mode involving many projects accessing the same data. In turn, this may be motivated by preferring to have a very large and relatively stable geospatial data system that is independent of the projects that are using it (and/or independent of the users that are using it; and/or independent of the software that is using it). It may also be motivated by needing to work on so many (100-1000) projects that even a small amount of common data between projects would lead to large amounts of wasted storage space duplicating the same data.
Not everyone works this way. But enough of us do that it should be an option. I teach Arc to college students; I use it in research; I've probably created 300 MXDs in my preferred use mode, which relies on absolute path names.
It's fine if relative paths are the default. But they should not be the *only* option.
None of the existing workaround are wholly satisfactory. Using "Save As" and moving folder references from within Pro is cumbersome and only solves half the problem. Using separate drives for data and projects is too restrictive. Scripts to convert relative to absolute paths would be cumbersome.