Bug or feature? Immediate download of linked .mov file from post.

Happy New Year, friends.

Was using Boost recently (Android, sh.itjust.works) clicking the thumbnail of a post that looked like an image of video.

Next I saw (a version of) my phone's downloads folder, where the .mov video had saved.

I was a little freaked that clicking a post thumbnail caused a file to immediately get downloaded and saved on my device - no prompt or otherwise.

The post: https://sh.itjust.works/post/52568758

Can I ask if this is intentional? Or a bug with Boost? Post was setup incorrectly? Or maybe the post's target doesn't 'stream' .mov videos as-such; just sends them to be saved. But still no prompt.