Reinvestment of Coupon in YTM

One of the EOD question ask for Effective return on 11% bond assuming its YTM changes from 11.5% to 9% in one year and coupon are reinvested at 6% (note YTM is 11.5%).

I always thought YTM assumes all coupons are reinvested at YTM rate, not sure why I had this notation in my mind?

http://www.economics-finance.org/jefe/econ/ForbesHatemPaulpaper.pdf

This link goes into details on how financial journals and professor use this assumption in YTM explanation.

Any thoughts/comments or is it just me with wrong concepts in my tiny brain.

YTM has nothing to do with what rate you actually reinvest at.