Step 10 did not say "get it to operating temp" and then add distilled water.
Step 11 stated to let it cool.
I do not see what you are referring to.
Also, if you ever HAVE TO depressure when hot ............ I have often opened a hot radiator cap w/ a heavy towel (doubled over twice) over the cap. Turn the cap slowly. The pressure bleeds fairly quickly. The towel absorbs the hot water.