Hi Jeremy,
When I create a gallery, the option is already on 'media file', but it createas a shortcode like
[gallery type="rectangular" ids="1450,1449,1448"]
I discovered a shortcut to create the correct shortcode. When I click on the dropdown and change it to the second option (imagepage) and directly back to 'media file' it creates the correct code you mention.
However, it's still a stupid thing to explain to others which I help with the websites, because it is already saying 'media file' and then you expect it to work.
Kind regards,
Willem