Under the hood, Apple converts the “/” to “:” in the Finder APIs. If you look at the folder content in the Terminal using the BSD tools (ls, stat, etc.), you’ll see the : displayed -
In reality, you should stay away from these special characters in file names for sanity on ALL systems:
~ ` @ # $ % ^ & * ( ) { } [ ] | \\ < > : ; " ' / ?And, then be aware of them so that your app can handle them once it is available in user-land.