Does anyone know why the hardware version of FMU V5 does not have IMU temperature heating function?
Because it simply wasn’t part of the design spec. V5x is factory temperature calibrated so not having a heater should not matter since the offsets at differing temperatures would be known.
You can always thermally calibrate your unit if desired. https://docs.px4.io/master/en/advanced_config/sensor_thermal_calibration.html