I used it as the proportion for a sidebar layout of a webpage, where the sidebar needed to be not too small yet smaller than the sibling container.

  .sidebar { flex: 1; }
  .not-sidebar { flex: 1.618; }

But imo using thirds would've worked fine. Hard to tell the difference, at least in this case. 67% vs 62%.

(https://wonger.dev/enjoyables on desktop / wide viewport)