I'm not sure what it would take to make a 20:1 Attenuator, but I do know the ones Pico have work really well. They are accurate and distortion free.
As for the secondary pickups, these are capacitive 10,000/1 attenuated leads that produce a really nice response. An RPM pickup for your DVOM is an inductive clamp and would not show you the same thing at all. Very useful though for syncing a parade pattern using the external trigger