I don't mean to say your theory is wrong..
...but that adage applies only to blade front sights aiming at 6 o'clock hold.
Most any other sighting system, and even a blade when aimed center mass, is not so affected.
I used to think the same thing. Less mirage, clear view makes the ring of white more pronounced so you hold higher. I get that. However; I think there is more to it, and here is my basis for that, and it makes some sense in the context of what the shooter says his conditions were like. (I'll get to that at the end)
Over the last couple of yrs I've managed to get my F-TR rifles tuned to the point that if there is vertical on the target it's not the rifle, it's either I pulled a shot or something on the range is causing it. I really started to notice this in Canada last yr. We often had really heavy mirage, I'd be holding V-ring vertical, the targets would go clear (sun behind a cloud) and bang, top of the 5-ring at 900 yds, every time. I started holding the bottom of the V-ring every time I saw it go clear. The US team noticed it to. In the Canadian Championship team match at least they would shut down the shooters if it happened in a team match. I wasn't on that end of the line in the FCWC to see what they did then.
Below is a target I shot a couple of weeks ago at 600 yards. I cleaned this, so did the shooter next to me. I ended up with like 9Xs, he had 13. The scorers told me after the match that he and I both got a high shots on the mirage change late in the match and he dialed down and I didn't. In this case we went from heavy mirage to clear.
In the case of the shooter above he had little mirage for the most part, but if it did pick up during the string, look at his vertical displacement. It is almost identical to mine, just in the opposite direction. with the opposite condition.He doesn't have any bottom of the X-ring shots, he's got two distinct elevation sets.
Granted, this is only two examples, but it seems to have merit here.
