Tim, that sounds like great advice. In the research I've done, there are very few mentions of testing the turning resistance of the spindle.
Here is a synopsis of the methodologies I have found:
Parktool site: Snug the drive (body) side of the cartridge into the shell, then tighten the non-drive (adjustable ring) side to manufacturer's spec (around 360 in-lbs usually). Done. They specify there is no need to torque the drive (body) side since the flange is against the shell and stops it when tight.
Barnett's manual: Snug the drive (body) side into the shell, then torque the non-drive (adjustable) ring to spec,
then torque the drive side to spec. Done.
UBI instruction: TORQUE the drive (body) side to spec after installing into the shell, then TORQUE the non-drive (adjustable) ring to spec. Done.
See why I'm confused?
Your method is different than any of these, but it makes sense to me to get that drive side in there good and tight, and then only tighten the non-drive adapter side as much as necessary, thereby not risking breakage of a plastic ring, and also not adding too much preload.