This type of solution works better at large scale where you have space and power budget for a lot more IMUs. Phones are very power and space constrained, so you

This type of solution works better at large scale where you have space and power budget for a lot more IMUs. Phones are very power and space constrained, so you only have room for 1-2 IMUs. In a car, 10W isn't a problem and there's plenty of room for higher power and higher quality sensors.