They improved the efficiency of coal?

Absolutely. Early engines were so inefficient that they could basically only be used in coal mines.

Massively. Extracting more useful energy from coal has always been a goal.

Very much unlike with software. Where the goal for long while is to burn as many resources as possible on end user devices.

I assume the reference was to the Jevons paradox, as described in Jevons' 1865 book, "The Coal Question". Watt's steam engine massively increased the efficiency of coal in steam engines, which increased the use of coal fired steam engines, which increased coal consumption.

Of coal use, yes. That's what inspired this: https://en.wikipedia.org/wiki/Jevons_paradox