/usr/obj and releases

[Colin Percival]

In src/etc/mtree/BSD.usr.dist, it says that /usr/obj should exist:
    41 obj             nochange
However, in src/release/Makefile, the doTARBALL specifically avoids
putting /usr/obj into a tarball, with the result that it will not
be extracted during release installation:
  1114 tar --exclude CVS --exclude obj --exclude BOOTMFS -cf - ${ARG} | \
                         ^^^^^^^^^^^^^

This discrepancy has existed since March 1995, so I'm guessing that
it isn't a mistake -- but can someone explain the reason for this?

Colin Percival