Matt Simpson was talking about people who have in fact reflected on their values a lot. Why did you switch to talking about people who think they have reflected a lot?
What “someone actually values” or what their “terminal values” are seems to be ambiguous in this discussion. On one reading, it just means what motivates someone the most. In that case, your claims are pretty plausible.
On the other reading, which seems more relevant in this thread and the original comment, it means the terminal values someone should act on, which we might approximate as what they would value at the end of reflection. Switching back to people who have reflected a lot (not merely think they have), it doesn’t seem all that plausible to suppose that people who have reflected a lot about their “terminal values” are often the most confused about them.
For the record, I’m perfectly happy to concede that in general, speaking of what someone “actually values” or what their present “terminal values” are should be reserved for what in fact most motivates people. I think it is tempting to use that kind of talk to refer to what people should value because it allows us to point to existing mental structures that play a clear causal role in influencing actions, but I think it is ultimately only confusing because it is the wrong mental structures to point to when analyzing rightness or shouldness.
CEV is not preference utilitarianism, or any other first-order ethical theory. Rather, preference utilitarianism is the sort of thing that might be CEV’s output.