I don't think the 1980's loonies were steel, they appear to have been mostly nickel.
I suspect though, that some detail of the various ways he did this just got lost over time. You could probably fish them out with superglue or sticky mastic on the antenna rather than a magnet, for example.
Or maybe the magnet was always used to hold some kind of trap door open rather than directly fishing the coins.
Article says loonie came out and implemented in their system in 1988. Before that it was mostly quarters. Both were nickel based which is ferromagnetic.
Loonies are coated in a different metal making them less magnetic, but stronger magnets will fix that.
I suspect though, that some detail of the various ways he did this just got lost over time. You could probably fish them out with superglue or sticky mastic on the antenna rather than a magnet, for example.
Or maybe the magnet was always used to hold some kind of trap door open rather than directly fishing the coins.