The exportfs tool contains multiple bugs.  In particular, it does not interact correctly with changes to /etc/exports, and in list
mode (i.e. no options or just -v) it does not correctly reflect changes to the list of exported directories.

Examples:

"exportfs -v" produces exactly the same (non-empty) list of exported directories before and after an "exportfs -ua", although
testing with clients shows that the directories were indeed exported before the "exportfs -ua" but not after it.

If an exported directory is wholly removed from /etc/exports, exportfs behaves as if it were still there.  In particular, it is still
exported by exportfs -a.  However, exportfs does seem to recognize changes in mount options in /etc/exports.

The above should be interpreted modulo the fact that entries present in /etc/exports at system startup seem to be treated
differently -- i.e. "stickier" -- than entries that are added later.