Ramzez - well I would definitely argue that both reporting leaving and reporting reaching levels have equal weight in preventing level busts. Both increase pilot and controller awareness. I can't find a specific statement for reporting reaching but you could cite section 4.23 from the following document from the same Eurocontrol Level Bust Briefing Notes.
http://www.eurocontrol.int/safety/ga...es/BN_Gen2.pdf
and argue that it is providing the controller with advance information.
On a separate note it is interesting to see the USA perspective as quoted by Radarking. There is a FAA/USAir study mentioned in the same documents. With 70% of level busts examined due to breakdown of pilot/controller communication loop, you would think they should be using its recommendations!!