The inspire and P3 have a feature if the compass gets bad data then it flicks the craft into P Atti then your on your own flying it, and it does this to prevent such thing as a flyaway. While i do think the P3 has a more sensitive compass maybe than the inspire with this safety feature is another story and topic.
fplvert, while you point out the bit you posted, it has been said again and again by blade that doing a compass cali every flight may do more harm than good.
I have a P2V+ V3. My quad will convey, through FPV monitor AND the drone itself, if the compass if off and needing a calibration. From my research, the P3 does this and more. It would be foolish of anyone to take off and fly when not getting green across the board IMO.