As mentioned in the blog post we do not expect to support TAR archives. There is no central directory in TAR, so indexing would be very expensive, and we would

As mentioned in the blog post we do not expect to support TAR archives. There is no central directory in TAR, so indexing would be very expensive, and we would not be able to support tar.gz anyway. ZIP was chosen mainly because it fits with the feature set. The alternative was that we developed a custom format or took another approach completely. This was the solution that in our eyes would be the easiest to implement for clients.