"Running In Tires:
When new motorcycle tires are fitted for the road, they should not be subjected to maximum power until a reasonable ‘running in’ distance has been covered. 100 dry miles (160km) is the recommended minimum (discount any wet miles covered)."
The need to discount any wet miles ridden implies that the running in period is meant to wear the suface of the tire.
Page 178 of Contenental's Technical Manual for Motorcycle and Scooter Tires (2013):
New tires have a smooth surface after the
production process, which gets abraded only
through the moderate breaking-in of the tires.
Sudden braking and acceleration, and hard
cornering should be avoided until the breaking in
process has been completed. Only after the
surface of the tire is sufficiently abraded is the tire able to build up its maximum grip level. The
tire’s size/information sticker should be removed
before the first ride.
Every tire needs a certain operating temperature
to ensure its optimal grip performance. To ensure
this, tires should be warmed up by riding at a
moderate speed at the start of each ride."
Call me crazy, but I'm pretty sure manufaturers don't publish rumors when advising the users of their products.
Racers charge hard on new tires because they are paid to be faster then the other guys. Being a second slower on any given lap can end up making a huge difference in how big the paycheck is.