Why Salayatana is ommitted in this mode of Dependent Origination?

Why Salayatana is ommitted in this mode of Dependent Origination? "If one is asked, 'Is there a demonstrable requisite condition for contact?' one should answer, 'There is.' "If one is asked, 'From what requisite condition does contact come?' one should say, 'Contact comes from name-and-form as its requisite condition.' http://www.accesstoinsight.org/tipitaka/dn/dn.15.0.than.html