Sandbox projects cannot be tested if added in the "Add additional projects" section or by using &add[]=

There was this issue with the Admin Links D7 sandbox project where launching it would fail because its type was not set properly. Well now this is fixed (#2057285: Change project type from "Drupal.org projects" to "Modules" so it can be listed at simplytest.me) and the sandbox is indexed so it can be properly launched at simplytest.me without any errors:

http://simplytest.me/project/1927644

The thing is that the same sandbox project cannot be launched along with other projects. Try this for example:

http://simplytest.me/project/drupal/7.22?add[]=views&add[]=1927644

...and you'll see that Views is added as an available module after installation, but the sandbox project is not.

This would work instead:

http://simplytest.me/project/1927644?add[]=views

...but this way you don't get to specify which Drupal core version you want to test. This does not work:

http://simplytest.me/project/1927644?add[]=views?add[]=drupal

...it fails with: The "drupal" project is not a module or theme.

Nor does this (Drupal core as main project / sandbox in the "Add additional projects" section):

http://simplytest.me/project/drupal/7.x?add[]=1927644

And of course you cannot test two sandbox projects at the same time. These for example fail:

http://simplytest.me/project/drupal/7.x?add[]=1927644&add[]=1420990 (none of the defined sandboxes are added)

http://simplytest.me/project/1927644?add[]=1420990 (only the sandbox defined first after the project/xxxxxx part is added)