You need to think a little more.
I’m working on it!
Therefore I would argue that no sighted comparison can ever be called objective. Many experiments have also previously suggested as such.
I would argue that sighted comparisons should be called objective, just not necessarily reliable in terms of correlation with other methods of comparison. The sighted comparisons are objective comparisons, as are the unsighted ones. While it is interesting, and I think telling, that the unsighted and sighted perceptions don’t always correlate well, it doesn’t move either of them into the realm of subjectivity. It’s only the part about a person preferring one of their perceptions over another that is subjective.
Once you bring human beings and their impressions into the equation you have lost objectivity and are now lost in the realm of subjectivity bias.
Humans and their impressions must always be involved. That's not the essence of what makes thing subjective. I agree with you though that repeatable and consistent perceptions through a variety of testing means helps us to interpret our perceptions better. Objectivity is not necessarily correctness. And correctness will only be determined by further human perceptions. I've given the example of flying an airplane without visual reference and no instruments before. A person can try to keep a plane flying straight and level by feel alone. They are using their perceptions of motion as an objective method of controlling the airplane to the best of their ability. A radar operator may have a different perception of how the airplane is doing. From their perspective on the radar scope the airplane may appear to be banking hard left and diving toward a mountain. Future perceptions of airplane wreckage on the side of that mountain correlate better with the radar operator's perception than the pilot's.