The pedelec sensor uses a Hall effect sensor to detect the rotating magnets but it also seems to read which way the magnets are moving as the pedelec does not work when you pedal backwards.
Perhaps its output is biased to mid voltage
(~2.5V) with no magnetic flux and is pulled high before being pulled low
(or vice versa) as the magnets pass in the correct direction:
And this pattern would then be reversed if the pedals were rotated in the opposite direction:
I once tried to measure the voltage on the pedelec signal wire but as soon as I touched my meter probes to the connector terminals the pedelec simply refused to work!
Alan