Images in fastlane directory / images fallback to en

For StreetComplete, I follow the fastlane directory structure for repo descriptions and images: /fastlane/metadata/android

For English, I put the images and phoneScreenshots here: /fastlane/metadata/android/en/images

Now, if I look into the json in F-Droid's index-v1.jar, I see that description and summary is parsed correctly for all the languages. All the images, though, are missing.

So, this seems to be a bug. Possibly related: #357 (closed)

Additionally, I see that in the index-v1.jar, there are unlocalized fields for description, summary and icon. Is it possible to define unlocalized images like phoneScreenshots, featureGraphic etc. as a fallback? Or will the images under /en/ be used as a fallback? If not, it would be great if this was the case. Do tell if I should put this rather into a separate ticket. I just thought that these two things belong together as they both concern the selection/parsing of images.