From the link you gave
NFA is similar to DFA except following additional features:
1. Null (or ε) move is allowed i.e., it can move forward without reading symbols.
2. Ability to transit to any number of states for a particular input.
These are the additional benefits that NFA gives but it is not always compulsory to use them. If we don't use them then it becomes just like DFA.
But if we use these added features we can't say it is a DFA.
So we can say that NFAs can act like DFAs as well as like something more than DFAs. In this context you can think like DFA as a proper subset of NFA.
Then " Every DFA is NFA but not vice versa" is true.