This is why I never bother to show EQ curves or spectrum analyzers. There's value in that from a scientific POV, but people's ears aren't scientific instruments.
Young ears hear differently than old ears. Trained ears hear differently than novice ears. Healthy ears hear differently than damaged ears. People hear things differently based on the size of their skull, eardrums, or ear canals. When you are deciding what sounds good to you, all that matters is what you hear.
IMO, people who insist that I should show EQ curves do so from a desire that somebody to be "right", but I contend that from a musical perspective there is no right. People who hear no difference are right....they do not hear a difference. People who do a hear a difference are also right.
If you gave the same amp to Eric Johnson and Albert Collins, and asked them each to adjust the settings until it sounded right, one would dime the treble and the other would turn it almost completely off. I like living in a world where we can have both Eric Johnson and Albert Collins.