I was attempting to set the umask of my fileContext and then do a mkdirs, but the umask wasn't applied as expected.
doneDirFc = FileContext.getFileContext(doneDirPrefixPath.toUri(), conf);
doneDirFc.mkdir(path, fsp, true);
It appears to be using the default umask set in the conf (fs.permissions.umask-mode) and overrode the umask I set in fileContext. I had the default umask set to 077 and set the filecontext umask to 007. The permissions on the directories it created were all rwx------.