OMG Christofle! I had no idea about this. I have been told this repeatedly, have three right now & love them. I'll be talking to the guys I got my watches from about this. Thanks for the info.
Think of it as waterproof vs water resistant. (No watch is actually water proof but have varying water resistances that are tied to gasket integrity, viscosity of the liquid and pressure subjected to the watch.) In the same way most watches simply vary in resistance to magnetic fields are not 100% anti-magnetic.
The term magnetic field resistant might be a bit less ambiguous.