I know when I started, I also felt I had way too stiff arrow, I found out it was my release. A sloppy release can show stiff and give false indicators. Also found out hte hard way too long an arrow can give false indicators of being too stiff. I got a dozen 32" cedars and was expecting a weak reaction. I cut them down to 30" and started showing weak, and had to cut to 29" which was just right.

Not saying this is your problem, just when following Brian Sorrells book, you need to be careful of false indicators. And your example of bareshaft tuning is common for beginners like myself to get false indicators.