Installation of round bike cadence sensor - in the end of crank screw?
Looking at the video (the English version I linked in the comments), there are several options for installation.  The sensor can act as a replacement for the dust cap found on many cranksets (methods 1 and 2). The dust cap sometime screws in.
This doesn't work if the dust cap and crank bolt are combined (as on Octalink, and similar to what you describe).  I don't think the sensor is designed to replace the crank bolt in that case, but even if it is, I'd be very cautious.  Instead the 3rd option (cable-tied to the inside of the crank arm) is probably the best bet