I always thought from my understanding of the terms normative and positive that revealed preferences are a positive concept. For example, saying Anakin prefers grass to sand (i.e. $U(g)\succ U(s)$) is a positive statement.
My thinking is as follows:
It’s a value free statement
It’s empirically objectively testable statement. We can just make an experiment where we give Anakin choice of sitting in sandy room vs grassy room and observe preference.
Independent observers would agree on the observed outcome Anakin picking the grassy room.
However, I encountered an opinion that since all preferences derive from underlaying values they are all strictly normative and considering them positive even in the strict sense of revealed preference is a fallacy.
Is the opinion correct? If the opinion is not correct how would you refute it? Just by stating my points 1-3?
Also I tried to find some sources that would discuss this but google scholar just gives me results that are unrelated to this philosophical issues. I looked in Julian Ress’ philosophy of economics, and Hausmanns anthology but I could not find satisfactory answer there either. Are there any good references for this issue?