Gentle bump - I believe this question is referring to a passage in Hopcroft-Ullman taken out of context. Refer to the last paragraph of attached excerpt. It seems to say without a transition for each alphabet, the automaton is an NFA - BUT, the resultant DFA will be very similar with just the addition of the dead states. i.e., it is true out of convenience, but not in a strict academic sense.
The key takeaway is from the passage is "we shall sometimes refer to an automaton as a DFA if it has at most one transition out of any state on any symbol rather than if it has exactly one transition".