There's an argument that it's good to avoid premature optimization - build your thing with something easy like rails or elixir and then if you run into performance issues rewrite those bits in something faster.
It's not about premature optimization. They clearly didn't know enough about Go when they decided to use it -- partly because few people do, but they did know that -- and they clearly don't know enough about Rust, either. They're stumbling from one hype to another based on sales brochures and bragging about it.
Again, Tech is full of such low-experience teams writing this kind of unimportant software and rewriting it every couple of years, and I guess it's good that someone volunteers as a lab rat for new languages (even if they do it over and over). But they're so inexperienced that they can't even see they're being snooty about their ignorance of their own requirements and tech.
