Oh really? I always assumed as I never thought horizontally centring was ever a huge problem. Vertical was the actual hard thing for a long time (which is something table cells could easily do since the beginning).

You caught me in that I didn't read the full article, but I read enough to see that it has this CSS which centres on both axes:

    body {
      display: grid;
      min-height: 100dvh;
      place-items: center;
    }