Good find- yes, it's a fun one.
Validation of worn-out tire reduced r.r.! They say 20% reduction.
It appears the good stuff starts on pg 122.
Hysteresis is the biggie for losses. Deep treads = more hysteresis.
Tread wear ratings don't translate into miles of life. Tires with lower tread wear ratings have shallower treads, which equals lower r.r.
However, tires with deep treads, when worn to the shallower depth, can be said to have the same r.r.