the myth of given is critique of foundationalist epistemology that basically asserts “data can never be given, but always be built”.
of course, nothing is simply “given” in nature. things have to be produced. (D+G would add “even production itself”).
but to go from this to “data aren’t ever real” or, worse, “data could be indefinitely different” is a stretch. analogies: a plane is produced, and is very real. a mobile phone can be produced in a myriad of forms, but they all pay respect to some invariances (you can’t make a mobile phone that violates, say, thermodynamics).