This is continuing the trend of cloud pricing driving system designs more than the underlying hardware. AWS overcharges for inter-AZ traffic between EC2 instances, but undercharges for inter-AZ traffic between EC2 instances and S3.
It makes perfect sense to design this way, and as your blog post mentions, people have made similar realizations for columnar databases, and map-reduce frameworks.
It makes perfect sense to design this way, and as your blog post mentions, people have made similar realizations for columnar databases, and map-reduce frameworks.