Goenka's answer seems to imply that Thich Nhat Hanh's mindfulness is directed either outward or to the external characteristics of the body, but that his own technique uses a mindfulness directed inward, because that is where the misery is: inside, and we have to come out of it.
I don't know much about Thich Nhat Hanh's teaching but he seems to teach anapanassati using that very term, so I don't know to which extent Goenka's answer was accurate, but he nevertheless gives his criterion for approval: it depends on which use is made of that mindfulness once developed: is it directed inward on subtle reality or only outward on gross reality?
Where knowledge ends, religion begins. - B. Disraelihttp://www.buddha-vacana.org
As a sweet-smelling and beautiful lotus flower may grow upon a heap of rubbish thrown on the highway, so also, out of the rubbish heap of beings may appear a disciple of the Buddha, who with his wisdom, shines resplendent in wisdom. -/ Dhp 58-59