The only person who is obsessed with this subject is you because for some reason you seem incapable of understanding how late birthdays work.
I've only heard the term "true freshman" referred to players playing in the NCAA in their draft year, as implies they are jumping up a level early and legitimately are doing something impressive, but perhaps I'm wrong on this.
My general point is that Buium being in the NCAA as an '05 is not special or surprising, just like it's not special or surprising that his other '05 born USNTDP teammates Smith, Perreault, Moore, Leonard, Nelson, etc... are in the NCAA.