That seems to just be one persons opinion, to say that is is rare to get selected first time for DEO is a load of crook, although I admit that if you have just left school it would be harder to prove you have life experience and leadership skills.
In regards to anyone getting in first time DEO 4 people and myself off my flight screening course are now in the services training as pilots and that was our first attempt, on my actual pilots course of 18, 1 was an ex NAV, 2 RAAF techos and 1 other guy it was his second attempt at board the other 14 of us were accepted first time DEO, 2 of whom had left school the year before so I think that puts that rumour to bed.