Olympic Airways does the same thing. Indeed it is mandatory for minors < 18 y/o to credit miles to parent's (s') account & one must be >18 to have one's own account.
I had a great flight & service on a 4-hr. flight ATH--LHR on March 16 in Y incl. free alcohol & a full meal.
Unfortunately, OA has no airline partners, so now I have 1994 orphan miles

, as I have no intentions of going to Greece again soon.