The answer that I got from Graphisoft on this question, a couple of years ago, was: There is no listing in the Python API of All the built-in properties or their Read Only status. The only listing is returned by the GetAllPropertyNames() function which will list Built ins as a 'Localized' type -- but this listing is not complete.
I doubt that Graphisoft would act on this request unless they get a larger number of requests to do so. It seems that Python development has been put on the 'back burner', but we'll see if this is so in 27?
Windows 10 - Visual Studio 2019; ArchiCAD 26