I certainly remember seeing in my online ground course i recalling having to get the name of Safety pilot and insome cases the cert #. though it did not mention the cert # of the flight instructor.
I think the reason why so many people may want the cert # is how would you know if this person is actually rated to fly this sort of airplane, or if this person may be a pilot at all, or in any cases you lie having a safety pilot and the faa asks you who is this, and youre in deep ****** if you can't get the 'person"