You and the manual are both correct.
On acceleration, where the manual is focused, lower lock points means the RPMs make their biggest drop sooner, reducing fuel usage but you take a hit on performance. Higher lock points keep the engine in the higher RPMs where more power is generated.
On deceleration, this is all opposite. Lower lock points keep the TC locked longer. This gives a better control of speed and improved braking (both engine braking, and forced higher RPMs helping the brake booster), a nice performance aspect useful in fooling around and towing. Higher lock points, as you mentioned, will allow the engine to drop to a lower RPM while decelerating.
Now before you jump up and program the max and mins, here is an important point. You have to keep the two points the same because every time the throttle is applied the TC would be locking, then if you let off it would unlock. The result would be unnecessary transmission work and an unsettling ride if you were to use cruise control.
Here is a graph I made a long time ago to show someone how the engine reacted to TC lock points being changed. Pictures are worth a thousand words.
