RED, I fully agree with what you have had to say on the subject.....
All those lenses begin at shade 5 regardless and that offers adequate protection from momentary flash at any rate.
Only a moron would continue trying to use a lense that failed to immediately switch darker....
And as I mentioned previously, the solar version similar to harbors unit has served me very well for last couple years....for me it has worked just great and reliably with no ill effects....For me it has proven to be a great product!
And I have done an awful lot of welding over the last 40 years and my eyes are very light sensitive....and especially so in recent years because I need reading glasses to see anything close up because of my age and I have to wear them as well when I weld or I cannot see what is going on in the puddle clearly.
If the lense in my "cheap'auto helmet was not working as it should, I would certainly have felt the effects of it, especially given the magnifying effect of reading glasses.....and mig/tig is primarilly what I do and as you know, those arcs are especially high UV and very bright!
and I can afford a $400 helmet.....but I have yet to experience the need....and I am not convinced that they would perform better!