Yeah, my bad, you are correct. Just tested with the preview and portrait pictures indeed do not show.

Disregard this comment, misread the parent

Just confirming that all 3 pictures also display correctly for me:

Oh, so that explains why the ratio of favorites/boosts is so low on mastodon. I thought it was just a culture thing, where people rarely left likes on posts.

Turns out it was just a software quirk.