You are sorely missing the point. You made the constraint the specific and only focus of the task. The example from the OP pertains to non-filename-related-tasks that have an additional specification added on to them. If your filenames need to be lowercase for all tasks, not just specifically filename-related tasks, you start running into problems.

> you're expecting to use it without steering

If I have to manually "steer" every mistake it makes on every trivial task, instead of being able to deterministically eliminate classes of failures so that fixing the task one time ensures that failure never happens again on similar future tasks, it is in fact faster to just type the fucking code myself.