One is for the basement, for leaks.
The second is to tell us when the tub is full! Just in case we get preoccupied while it is filling… the wire sensor away from the device body is perfect for this application. It’s a 2-person tub. I will position the unit with 2 clips for the wire mounted on the edge if the tub, such that one position indicates when the tub is full for one person and the other (at a lower water level) for two.