Big projects are routinely ported once or twice to new languages. Normally, moving a project from one language to another entails a full rewrite. Because the process of building their own language had the side effect of instrumenting all their code (the transpiler was custom-designed for their application), they were able to write a program to do the port for them. That's a win I don't see captured in the original blog post, and that's all I'm pointing out.