It's good to be safe. There is a previous thread on this, but I cannot find it now. Let me first just show my source. Ralph Chou is the eye safety expert used by NASA, the American Astronomical Society (AAS), and Sky and Telescope. He wrote the eye safety section of the new ISO standard, ISO 12312-2, on filters for direct observation of the Sun. Here is his updated document on the AAS Web site https://eclipse.aas....-Eye-Safety.pdf . See the section on welder's filters. When Rainbow Symphony cites a safety standard on their glasses, it is Chou's standard that they are referring to. When we talk about not using Baader film for direct observation any more, that is also Chou's new standard.
But that document ends with this advice, "This paper does not constitute medical advice. Readers with questions should contact a qualified eye-care professional." ed_turco has done that, and his qualified eye-care professional feels it should be dimmer, and he could very well be right. The fact that the new standard is more strict than the old standard makes you wonder if the next standard will be even stricter, and if eventually a #12, #13, or even #14 may someday be realized to be unsafe in ways that we cannot guess today. So you need to draw your own conclusions.
The reason I carry the #12 is that at least today the ISO standard considers it be safe (whether it is or not), and carrying it definitely increases my safety. When I am trying to position the sun when it is in the clouds or haze or at the horizon, I used to squint or look quickly. The #14 just looked black in those circumstances. Now I can look more safely through the #12.
The rule of thumb I learned was not to stare at anything brighter than grass in sunlight. So I would not normally use the #12 straight-through for an overhead sun.
For average eclipse-goers, a #14 makes more sense. Frankly, purpose-made eclipse glasses make the most sense to me, and that's why I bought them for the group. At 85 cents each, I could afford them.
One thing I do worry about is in places that happen to have partly cloudy skies or very thick haze, naive viewers will not see anything through their eclipse shades and will attempt to see it while squinting or looking quickly. Or worse, use something at hand that dims the sun without blocking ay UV. Squinting and unknown materials are clearly unsafe. Same reason you can get a sunburn on a somewhat cloudy beach day.
And let me end with a similar caveat. I am not a solar safety expert. I am showing you the research I have done for my own eyes. You need to do your own.