Well yes. But in this case that is the problem no? As a developer I have to upload new binary when changing screenshots, thus forcing my users to redownload a n

Well yes. But in this case that is the problem no? As a developer I have to upload new binary when changing screenshots, thus forcing my users to redownload a new version. A diff of an identical binary would be zero (or something very small as at least the build number would have to be updated). For developers it would be better too but Apple has always privileged user comfort over developers.