We see that there is a car in the distance with headlights that overlap each other:
Now when he applies the filtered lens -- Surprise surprise, the headlights still overlap:
I understand the point. It's very difficult to correctly estimate the size/shape of a bright light at a distance because of things like glare.
The problem with your point is that you are comparing headlights and glasses to the sun and a solar filter. It's been my experience that the two are significantly different.
I drove to Wyoming during the Eclipse. August 21, 2017.
I would look at the sun with my solar filter on. I would see that 50% of the sun was blocked. I would use my phone camera or just take a fraction of a second glance at the sun which still appeared to be a blinding giant ball of light the same size and shape as always.
Even when the sun was 99.95% blocked by the moon if I briefly glanced at the sun with the naked eye (or with my phone) the sun was still a giant blinding ball of light.
The problem here is that, with the solar filters, I was able to easily see the shape of the eclipse and see the percent of the sun that was being blocked by the moon.
Based on my experience with the solar eclipse and solar filters I believe that you can make a MUCH more accurate measurement of the size of the sun.