Why would we use iron filings to display a magnetic field interaction and then teach this as the unaffected field of a magnet?
Iron affects the field itself. This is analogous to an observer affecting a quantum event through observation.
Magnetic mappers that contain iron anywhere near the proximity of the target to be measured are inherently outputting false field information.
Where are the true examples of unaffected fields? Could they really be different than what we have been taught?