Only one problem with that method. He is allowing the Inspire (and gimbal) to initialize at an angle that is outside the flight parameters of the aircraft.
The IMU needs ZERO movement to initialize properly and the chances of a bad calibration are many times increased by doing what he is doing.......
I would not want to fly that Inspire straight after that

Of course, he could then do an IMU calibration but that will take 5 minutes to complete..... add that to his 3 minutes set up and it's taken him 8 minutes.
I think I will stick with the slow methodical method...... My $3,000 is not worth risking for an additional 60-90 seconds it takes to go through the 'power on, out of travel mode, power off, attach gimbal, power on' sequence....... but that's just me.