I gave it some thought and in my opinion this isn't a bug. I think a lot of gifs do not loop but users are used to gifs looping so the app auto-looping gifs should be considered a feature.

To handle edge cases like this, I think it's better to just add a setting to allow the user to choose between looping gifs automatically or to use the GIF loop metadata. I added an item to the roadmap for this.