List module releases that are "Recommended by the project’s maintainer."
As described in Update status XML, Drupal.org returns information about project releases, including the recommended major version, as XML output. For example, the first XML elements returned from https://updates.drupal.org/release-history/imagemagick/8.x are the following one.
&lt;title&gt;ImageMagick&lt;/title&gt;
&lt;short_name&gt;imagemagick&lt;/short_name&gt;
&lt;dc:creator&gt;sun&lt;/dc:creator&gt;
&lt;type&gt;project_module&lt;/type&gt;
&lt;api_version&gt;8.x&lt;/api_version&gt;
&lt;recommended_major&gt;3&lt;/recommended_major&gt;
&lt;supported_majors&gt;3&lt;/supported_majors&gt;
&lt;default_major&gt;3&lt;/default_major&gt;
&lt;project_status&gt;published&lt;/project_status&gt;

&lt;recommended_major&gt;3&lt;/recommended_major&gt; is referring to any version matching 8.x-3.*.
Unfortunately, that information isn't returned from https://updates.drupal.org/release-history/imagemagick/current or any URL matching https://updates.drupal.org/release-history/*/current.
&lt;title&gt;ImageMagick&lt;/title&gt;
&lt;short_name&gt;imagemagick&lt;/short_name&gt;
&lt;dc:creator&gt;sun&lt;/dc:creator&gt;
&lt;type&gt;project_module&lt;/type&gt;
&lt;supported_branches&gt;8.x-3.&lt;/supported_branches&gt;
&lt;project_status&gt;published&lt;/project_status&gt;
&lt;link&gt;https://www.drupal.org/project/imagemagick&lt;/link&gt;