It should be outcome-based at every level, not just engineering.
Time boxing as a group (e.g. scrum poker) is useful for preventing a leader from underestimating time required for a task, which is a necessary safeguard on most teams when the engineer will be penalized if they don't meet a deadline, rather than a leader being penalized for setting too short of a deadline - even if this is the n-hundredth missed deadline by a report of theirs.
Time boxing as a group (e.g. scrum poker) is useful for preventing a leader from underestimating time required for a task, which is a necessary safeguard on most teams when the engineer will be penalized if they don't meet a deadline, rather than a leader being penalized for setting too short of a deadline - even if this is the n-hundredth missed deadline by a report of theirs.