[tor-relays] Delete keys on reboot

The Tor Relay Security document suggests deleting keys upon reboot to prevent one-time key theft. I have tried to do this in Raspbian via cron but have been unsuccessful. The cronjob I have running is:

@reboot rm -f /var/lib/tor/keys/* && echo "keys gone!" > /home/[me]/reboot.txt 2>&1

I have the echo as a debugger. When I changed /var/lib/tor/keys/* to /home/[me]/test/* the job runs successfully. When changing it back to /var/lib/tor/keys/* it does not.

Is this something I should resolve? If so, is there something with my cronjob that's preventing it from working?