Why did DSM-5 and subsequently ICD-10 allow personality disorders to be diagnosed in children I was fine with the theory personality characteristics are so highly variable under the throes of adolescence that it is a practical impossibility, if not clinically inappropriate, to diagnose  such disorders until the age of 18. I'm aware that antisocial personality disorder hasn't changed.

Too many practitioners see a personality disorder diagnosis and turn off their brains to the likelihood of a mood, anxiety, or psychotic disorder.

Specifically, why is the new criteria considered better than the old criteria under DSM-3 and -4?
An article on the NCBI website states


  Many clinicians are reluctant to diagnose personality disorders (PDs) during youth, viewing paediatric personality deviations instead as reflective of given developmental stages. This is so despite evidence that certain youth are indeed at risk for the eventual development of PDs as adults. Unfortunately, late identification of these disorders prevents timely treatment and potentially increases morbidity.


There are also a fair few references to articles backing the idea up