The appeal to the old "science doesn't know everything yet" is one used as a partial justification by every pseudo-scientific/supernatural/fringe belief system.
It's an exceedingly weak justification for believing in dubious ideas.
The patent offices are full of patents for Perpetual Motion Machines by the folks saying "Science doesn't know everything!" It doesn't make claims for a perpetual motion machine an inch more credible. What WOULD make it credible is actual evidence such a machine could or does work! Otherwise you just join the extensive line up of people thinking "I've discovered a new reality" and grumbling about how science just won't recognize their claims.
So, take a conversation I (and others) had with an audiophile who spent over $1,000 on a "high end" HDMI cable to replace his off-the-shelf HDMI cable. He claimed it made the image obviously sharper, obviously richer in color and higher in contrast.
Now...this is literally impossible given how HDMI cables work. He had not upgraded from an old spec HDMI cable to a newer 4K spec'd cable, and hence this was not due to a variable like he was now passing through 4K/HDR images where he wasn't before. The claim was that these were the same spec cables, the original was working, but the new one, as claimed by the company that sold it to him, "improved" the picture quality. It was pointed out this was impossible (unless they had inserted an active chip to alter the image, and didn't tell anyone).
In evaluating such a claim, what is more plausible? That this individual had discovered that the very theory by which HDMI works, the very theory that has allowed the successful manufacturing and deployment of that technology the world over for many years...is actually wrong? Or...given the fact that every human being has the propensity for bias to affect their perception...that his perception was influenced by a bias effect? This is similar to choosing between the likelihood that someone had really made a perpetual motion machine in their garage, overturning basic physical theories, vs their claim being error or bullsh*t.
Nobody makes a dubious claim more likely by crying "But Science Doesn't Know Everything!"
And when you mention "50 year old measurements" that can be a feature, not a bug! If someone wants to say the electronic measurements that have, for instance for cables, been so reliable, and used with predictable results in such a truly vast array of situations around the world...that these ways of measuring are "wrong" or "insufficient" then they take on a substantial burden of proof!
Anecdotes of "I'm sure I heard something" will hardly do! They should at least offer plausible explanations to begin with (and not ones that can be easily undone by someone with expertise in the field) or failing that at least demonstrate that they CAN actually hear this difference they claim.
In other words, can they hear the difference when they are not peeking? In blind tests controlling for sighted bias? That's a component that your OP misses as well. Measurements aren't the only tool in the box. One can indeed demonstrate something can be heard that isn't showing up in measurements. But given the consequences of such a claim, it makes sense to first establish people ARE REALLY hearing this difference, under controlled conditions.
Of course, we can all think we hear whatever we do, and practice this hobby however we want!
But...if someone claims to hear things that are dubious under current theories of electronics and human hearing thresholds, and offers no objective/testable evidence, nor any testable claims (won't show it via blind tests), then they have only themselves to blame for just shouting in to the wind, and placing themselves in the long line-up of fringe theories which also have not passed any of the normal crucibles for reliable knowledge.