Why is the built in preview not working when utilizing the 'content by label' macro?

[Thomas Berger]

When using 'content by label' to compile a list of content, the attachments (PDF) are not being previewed but downloaded right away.
The preview function is working when I manually reference a PDF attachment on a page.
Why is content by label not allowing the preview. This is a strange user experience (UX)!
We don't want the attachments to be always downloaded, since that takes too long and user will keep outdated versions on their computer.

How can we get the preview working for content type 'attachment' when using the 'content by label' macro?

[AnnWorley]

It doesn't work for me on my Confluence 6.2.3 test instance, either, so I opened this suggestion for the dev team: As a user I would like PDF attachments to preview when displayed via content by label macro

I started to open it as a bug but I am not sure whether the intended behavior is to preview or download. As you pointed out, it is certainly an inconsistent experience as .png images do preview just fine in the content by label macro.