Don't know if this has already been mentioned. If so, disregard.

Let say your runtime is a geometry folder and a character folder. Let's say that your distribution has a geometry folder, a character folder and a hair folder.

In Windows, the geometry and character folders are consolidated with the existing folders and the hair folder is added. In MacOS, the geometry and character folders OVERWRITE the existing folders and the hair folder is added. It has been maddening to adjust to this.