It uses a dual frequency GNSS receiver with GPS, GLONASS, Galileo, and BeiDou. There are claims of 6mm accuracy, but for a smaller excavator in real world conditions a couple inches is more realistic. Plenty accurate for digging a pool though. The precision and accuracy for blades is much better than for excavators/buckets.
I have plenty excavators with 1/2” accuracy at the bucket teeth out there working.
But yes an inch to two is good enough for digging a pool. If you used laser to augment then you can get down to the knats-butt.