[opensuse-packaging] Package publishing: per target or per arch?

I am a bit unclear about the rules for when build packages are pushed to repositories. I have been told that it only occurs for a given build target when all architectures for that target have finished building. However, when I look at download.opensuse.org, it seems packages are getting pushed from one architecture while another is still building according to build.opensuse.org.

So I was hoping to get a better understanding of how OSC decides whether to publish a package. It is important because it has an impact on how we structure our build targets.