(it also reports the disk usage for
. which will be the sum of the disk usages reported for the subdirectories, and that of the non-directory files in the current directory).
zsh and any
du -sk -- *(/D)
In any case, while that doesn't report the disk usage of directories at depth
2 or below and their contents, the disk usage of those are still included in the disk usage reported by for the top level directories (in other word, there is recursion).
That's one of the potential meaning of the size of a directory. In other words, that's the disk space that would be reclaimed if that directory and its contents were to be removed (assuming the files have no hard links outside those directories, and that their data is not referenced (possibly in part) in other files outside those directories), note that it's generally different from the sum of the apparent size of the files themselves (including directory files) as reported by