I agree but it seems not uncommon particularly for small devices. When I had a Garmin Watch for a few months (early 2024 model) t also has a custom cable described by Garmin as "Charging/data cable" and the one I got has a USB-C plug on the other end ie same situation as the OP's Wahoo device. But I can see (certainly in the case of the Garmin Watch) that even a USB-C watch end connector might be a bit bulky. But from my Polar HR check monitor device I think a USB-C at the sensor end would fit fine.I agree that it is wrong not to supply special leads such as that magnetic one. I would be annoyed too!
Ian