As i wrote earlier, i'm always happy to learn someting new.
About the inductive pickup testing: i haven't heard about this specific
method, but i belive it's working good. (I used to test the pickup
in it's place with an oscilloscope during cranking.)
As the "stalks" of "T" shaped magnetisable (this is important) metal
runs over the magnetic field of the pickup, it's generates voltage
in the pickup coil, which can be measured (either a digital multimeter
in AC mode or with an oscilloscope). The voltage and it's frequency
will be proportional to the drill RPM. Try to keep 5mm (0.2in) gap
between the pickup and the revolving metal piece.
The drill and the pickup has to be fixed correctly otherwise the pickup
pulls itself to the "T"-piece.
Check the resistance between the pickup's connector. Note the pins
where you can measure about 0.5-0.6 kOhms. Later when the test bed
is ready you can measure the pickup output voltage between these pins.
I hope this is anwsers your question.