when it idles it does not give motor enough oil to lube it.
and that 10hr break in is for oe piston,(cast) plus oils we have now are better, compared to back then.

i did heat cycles 110 first then 125, you keep reving the motor, the entire time. dont let it just idle.
then i rode it around after that, just keep it under full thrtl,

this is my $.02 tho, take it how you want to. everyone has there own way. i used to have a friend that was a pro rider
when his dad would put new piston in his bike, josh would start it and ride it to the starting line. no break in for his stuff
it was done on the track.