In Kingdome Come, Supe's has his classic symbol initially. He only swaps to the KC symbol after the DP attack and Lois dies. But Ross didn't just use the same shield and swap the gold out for black. There's more to the design then that. I think this Reddit comment nails what Ross was going for;
Which is always how I've interpreted it. Its stripped back because that Supes had lost so much. It makes no sense on young Superman.
I know we've all done a 180 on the suit with the set pictures, I have as well...
but that shield.... It looks less like a symbol, and more like a corporate logo.