MP/M had a similar feature that was more of a necessity, since several users could be logged on simultaneously, each with a different user area. Given that CP/M is a single-user system, the need for the same feature is less obvious.
So "public files' don't show up with DIR commands, unless the exact file name is specified?
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(digression)
It's an interesting problem shared by a lot of operating systems. One system that I worked with started each session/job with no user-local files. At end of session, local files were all disposed of (i.e. printed or punched or deleted). If one needed a common shared (permanent) file, it would have to be attached to the session and given a local name and would be detached at the end of session. Of course, user-specific passwords were provided for each permission granted (read/write/execute). A local file could be made permanent by explicitly cataloging it with a distinct "catalog" name. There wasn't a lot of cross-contamination. System files were maintained under a separate management system and could not be easily changed (deleted or created).