That's why they (the surviving crew of the same briefing) were surprised to see the 26 mile cross-track 'error' on the INS when they found where they were in a less malign form of 'VMC', on a similarly briefed flight
And yet this didn't cause an outcry. Barely a murmur. But if the safety of the flight depended on the INS track, don't you think it should have?