I've found a confusing behaviour in Linux's version of du(1).
du can take a single folder to recurse into, or list of files/folders either via
--files0-from or in
But its behaviour is inconsistent if this list contains parents and children.
- A child given before its parent makes the parent count as empty
-d 0), a parent given before its child (vice versa) skips the child
OpenBSD's du conversely has consistent behaviour: it always outputs one line (or block of lines, if not given
-s) per input, and always counts everything as full-sized, parent and child.