the places where I've seen people leverage the folder-level permissions in Perforce (in the games industry) would be like: a contractor that provides art would only have access to the portions of the project that relate to the art they're working on but not the code; translators might have read access on one directory and write access on another directory. In academic settings I've seen Perforce used such that an instructor has read-write access on a directory and students have read-only access on the directory, and then each student has a subdirectory where they have read-write access and everyone else has read access, so that everyone can play each other's games. You can do stuff like this in git with submodules but it's somewhat complicated and difficult to teach to non-programmers. It's not really clear what the target audience is for the project. The mathematical/theoretical foundations are clear, but the target audience is unclear, so I'm not sure if these are use-cases that you consider to be within the project's scope or not; just sharing how I've seen the permissions models used in the games industry.
oh and nearly everyone hates using perforce and its clients p4v and the p4 command line, so it’s not like there’s no appetite for change. There’s very much an appetite to see Perforce unseated, because it costs money and is also bad.