As you know, Chakster, the magnet is in the cartridge body, not the stylus assembly
I am surprised you said that @lewm
This is Moving Magnet principle.
1) Now I want to show something, see what’s inside the replacement stylus assembly carrier HERE. ****
We’re talking about Moving Magnet cartridge (Pickering), not a Moving Iron.
2) I have mentioned Stanton/Pickering’s Samarium Cobalt magnet because it’s not always a choice of some other MM manufacturers, here is Alnico magnet in MM design for example ***
Another example is Audio-Technica MM with two magnet right in the replacement stylus assembly. Yet another example from Ortofon MM.
P.S. The difference between MM, MI and MC explained here in motion.