The inclusion of the word degrees was suggested as good practice from an ongoing investigation of level busts. If my memory serves me correctly, a significant number of level busts occured when a climb/descent and turn were given in the same transmission, as in Zkdli s example. Often the readback would be correct - instant response - and then the transposition would take place - active response. The first the ATCO knew about it was as the level bust took place. Including the word "degrees" after the figures was meant to emphisise which was which, as it tends to be the last thing heard that sticks in the mind longest.
I agree it is good practice, but feel that ATCOs should not rely on such devices. If the circumstances arise in which a heading is more likely to be mistaken for a level and particularly if the results of such a mistake could be catastrophic, use a heading ending in five or make two transmissions.