I think it referred to the classic efficiency vs latency tradeoff. Like when emergency vehicles are always on standby, which is inefficient, but allows them to roll out without delay. Conversely privatised rail lines squeeze out every ounce of capacity from the infrastructure resulting in delays when something, anything goes even slightly wrong.
I use this extensively when planning activities with my children. It's a fun challenge because they're both too young to tell the time, much less read, which are constraints one does not normally encounter in their work life.
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.
I use this extensively when planning activities with my children. It's a fun challenge because they're both too young to tell the time, much less read, which are constraints one does not normally encounter in their work life.