If you're looking for the magnet that is attached to a spoke on many bikes, I don't think the Allants have one. I think they are built into the brake rotor. Check
@Court review:
Price: $3599.00 | Model Year: 2020 | A great all-around electric bike that's capable on city streets and light trail, it replaces the Trek Dual Sport+ from earlier years. Proven Bosch Peformance Line CX motor with shift detection. The high-step frame has mounts for adding a second battery pack...
electricbikereview.com
Trek, Shimano, and Bosch probably worked together so that the rear wheel speed sensor could be mounted to the disc brake rotor mount vs. the wheel spoke. This means the sensor will be more durable and read with more accuracy over time. It won’t imbalance the wheel or make one spoke loose over time… it’s a great little upgrade