It's over simplified in their instructions. There's so many combos which can work, they just centered on 10 degrees as an example and because the FItech unit only has 45 degrees of advance allowable, it's relatively safe. They also assume that most operation will be done around the lower timing ranges, which is true of a street driven car.
Each user should strive to understand the issue (as you obviously do) and tune/setup accordingly.
If your gears put you at 3000 rpm on the highway, and you do a decent amount of driving there (like me) then your phasing should be close at that amount of timing. If your car is setup for the dragstrip with a huge-by-large stall converter, then phasing for 5-6k might be more reasonable. Likewise for those that tool around under 2500, setup for that RPM.
I can't wait for a decent Coil Near Plug setup to eliminate the spark distributor on my car.