It appears that bearing life is in reference to electric motor bearings. The magnetics of some types of electric motors can magnetize the bearings or the shaft. Metal debris is attracted to the magnetized bearing and starts causing damage inside the bearing or bushing the motor shaft rides on. Reliability of large motors is an entire field of study, primarily for factory reliability.
https://easa.com/resources/resource-...ing-failures-1
I did find one reference to demagging combustion engine parts. It appears that the concern is similar, metal debris sticks to bearing surfaces and cannot be easily wiped or blown off.
https://www.engineprofessional.com/TB/TB022318-1.pdf