If anything, it's the opposite. With a proper harness you stop having to spend so much energy reviewing every little intermediate step, and can focus on the higher level.
I'm actually working on a project now where the biggest problem I need to solve is that the verifier that reviews the test harness is too strict.
I keep being told that a proper harness makes agents better, but no one has shown me exactly what is it that gives them such amazing results.
Yesterday Gemini burned 40 minutes trying to diagnose a failed Expo build and going into loops of changing the Podfile and re-running the build, when the issue was that Xcode needed updating (quick Google search for it).
But my comment on burnout stands. The lack of downtime and dynamic thinking modes (admin, planning, review, actual coding) seems like it would conspire to make you either cram out more work or disconnect from it. Both of these become dangerous, after a while.
(Information workers were productive 4–6 hours a day, and the economy did just fine.)
I'm actually working on a project now where the biggest problem I need to solve is that the verifier that reviews the test harness is too strict.