Ah yes. Well. Ahem. Er. ...
I don't have that enabled.
BUT: Good news. I was able to rename the file called 'voicecommands.backup' which had a date modified time stamp from a couple hours ago (i.e, renamed it to voicecommands.xml), and that successfully restored my previous commands. Hurrah!
I assume that if I'd edited the new command tree and saved it, however, that would have overwritten that backup file, though, right? So it's not something to count on.
If this happens to others: I also had to re-enable the various plugins that my previous custom commands used, since my options.xml file was also overwritten when I applied the standard configuration.