Should OF be pure GTD? I hope not, because even out of those who admire and aspire to GTD, only a small fraction have achieved pure implementation. Many people are working their way towards that goal, or have found some happy stopping ground along the way, or even fall off the wagon and get back on repeatedly over time. For instance the
great article and feedback discussion the past couple of days at 43 Folders shows lots of examples of people in these different states of adherence.
I think Omnigroup are picking the almost perfect focus when they design the product around the GTD concept, but allow for flexibility and variations in needs and work style and orthodoxy.