the default DietPi install does not install those extra commands, so they are not available.
If you use our upgrade script for Pi - it should fail to upgrade and tell you to use their update mechanism, but it will as a bonus add the commands for you... Alternatively the commands used to generate them can be run manually
echo "journalctl -f -n 25 -u node-red -o cat" > /usr/bin/node-red-log
chmod +x /usr/bin/node-red-log
echo "dietpi-services stop node-red" > /usr/bin/node-red-stop
chmod +x /usr/bin/node-red-stop
echo "dietpi-services start node-red" > /usr/bin/node-red-start
echo "journalctl -f -n 0 -u node-red -o cat" >> /usr/bin/node-red-start
chmod +x /usr/bin/node-red-start
Note: they are not 100% identical in that they are are calling the dietpi-services command but hopefully are close enough.