> Saying the model failed to write a competitive C compiler makes more sense.

Their compiler fails to compile (well, at least link) some C programs altogether, and in other cases it produces code that is 150,000x slower than a real C compiler with optimisations turned off (interestingly, the model trained on the real compiler's source code). That's not "not competitive" but "cannot be used in the real world". But even more importantly, the compiler cannot be fixed or evolved. It's bricked (at least as far as today's models' capabilities go). For any kind of software, not being able to improve or fix anything or add any new feature means it's effectively dead.

You could not use it in production even if no other C compiler existed.

> Their compiler fails to compile (well, at least link) some C programs altogether, and in other cases it produces code that is 150,000x slower than a real C compiler with optimisations turned off

I would bet that those things are also true of at least one expensive commercial C compiler.