There are two subtly different kinds of efficiency:
1) How little input resources are used to produce a given amount of output. Tools that let you spend one hour to do a task instead of two fall in this category. As does growing twice as much wheat on a given plot of land.
2) What fraction of resources aren't used productively at all. The "slack" from the article, or wheat that gets grown but not eaten.
Improving the first kind of efficiency is usually a good thing. The second can also be positive, but only in moderation. If you try to reduce slack too much then you'll end up with systems that are brittle and have serious failure modes (like famine caused by wheat production being lower than expected)
1) How little input resources are used to produce a given amount of output. Tools that let you spend one hour to do a task instead of two fall in this category. As does growing twice as much wheat on a given plot of land.
2) What fraction of resources aren't used productively at all. The "slack" from the article, or wheat that gets grown but not eaten.
Improving the first kind of efficiency is usually a good thing. The second can also be positive, but only in moderation. If you try to reduce slack too much then you'll end up with systems that are brittle and have serious failure modes (like famine caused by wheat production being lower than expected)