I assume that BMW does not have enough inventory for these DEF tanks because they are failing at a much higher rate than they expected AND/OR they may be redesigning some of the sensors do to the high failure rate.
So it appears these tanks have temperature sensors, level sensors and a heater from what I gather.
Here is a picture of the tank with some of the senors.
https://www.ecstuning.com/ES254461/
I have passed on Diesels for my vehicles and I am not no hurry to get in line.