What is the discard option in `stty -a`? It uses `^O`

In stty -a, there's an option for discard = ^0. I've googled around, and the closest documentation I get is from: http://www.tldp.org/HOWTO/Text-Terminal-HOWTO-17.html which says

^O flush (or discard). Not yet implemented in Linux (but proposed). Sends output to /dev/null.

I tried it several times and nothing happened. If it isn't implemented, why is it bound to ^O then?