If you define having a particular value system, as a bias, then I agree. But I'm not seeing any fallacy here. The grandparent is stating that as long as we have a belief/value system where IQ/beauty is valued, then in a situation where all other things are equal, then IQ/beauty should be valued more.

That's not an unexamined or implicit belief, and intellectual rigour is in this case only relevant when applying it.

Where is the is/ought fallacy in that reasoning?