I agree efficiency vs latency, but it's also "exploit vs explore" balance, work/life balance and more, leaving time for research, exploration, shooting the sh*t, decorating the office, buying christmas gifts at lunchtime, helping out co-workers etc.

I think "slack" is a much more general concept than efficiency vs latency. The slack itself allows low-latency response to emergencies but the activities that fill the slack time can be valuable in ways that often aren't legible to the org hierarchy.