The manual assumes the builder is using a teeter balancer. Since the wings are staggared, the teeter fits between the wings better upside down.
When using scales or load cells all of that nonsense about upside down goes away. The days of balancing heavy expensive models with teeter balancers will come to an end once you've seen how easy weight scales work.
I demonstrated the process at JOK this year on the largest jet at the meet. No way anyone would have risked putting that jet on a CG machine! We used office scales and a calculator.