Not only is Fi about values, Ti can be as well. All Judging functions are, the difference is that the Extroverted Ones have a collectivist mindset and the Introverted---an individualist. Ti/Fi are concerned with the values of the individual and Fe/Te--societal values.
You are right about how NFs and NTs use ethics differently. NFs tend to apply them more, whereas NTs may use the T to find their values but they would make their decisions based on what they think make senses and not what their values tell them would be right.