When Fast Mode Helps and When It Doesn't

A team lead reads about fast mode and instructs the whole team to "turn fast mode on for everything, it can only make things better." Evaluate this instruction.

1. Explain precisely what fast mode changes and what it doesn't, and why "it can only make things better" is not accurate.
2. Identify two realistic work patterns on this team where turning fast mode on would be actively costly with little or no benefit, and explain the mechanism in each case.
3. Propose a better team policy that captures fast mode's actual value without the blanket downside.