Alexi, thanks for performing that experiment. That's a huge help. I think your broiler works a little differently than mine, but it still proves that 1/2" steel can definitely produce a Neapolitan bake time.
Are you using the broiler during the bake? I know, in the past, you've talked about the convection feature, but are you broiling as well? If you need to increase the top to bottom heat ratio, just move the pizza closer to the broiler. With close proximity (less than 4"), you should be able to pre-heat the steel to around 600 and get the same kind of 2ish minute results you're getting with cordierite, plus... you should be able to cut your pre-heat times in half.
Mark, nice pizza. I'm really surprised that 40 seconds of broiling would pump that much heat into the steel. What was the bake time?
If I had to choose between this pie and page 3, I'd go with page 3

Not really because of the color or the charring- both look fantastic, but more because of the thickness factor. I gravitate towards a much smaller rim.
The pizza that I grew up with was soft/not crispy and, when I say, pale, I mean really pale- almost pure white, with a few brown specs on top. Not char, but not golden brown. The bottom would have a little char, but not the top.