Smaller systems are frequently discussed as compromises. In a well-defined workflow, they can instead be the more deliberate choice: faster to run, easier to constrain, and inexpensive enough to evaluate continuously.
The important design decision is placement. A narrow model should receive a bounded task, the context required for that task, and a clear route for declining work outside its competence.
Knowing where the work ends is not merely a safety property. It is part of what makes the tool useful.