They say in the fine print:<p><pre><code>  Same-sex occupation&#x2F;relationship matchups weren’t common enough to reach the top five in any occupation.
  So the chart also highlights the top male-male and female-female job matchups for each occupation.
</code></pre>
In other words, female -&gt; female pairings are overemphasized in the chart, otherwise you would not see them at all.l