Unfortunately different things are currently called "mission efficiency" in the game.
Right.
The HoI4 development team's use of English words in a sloppy way does indeed introduce confusion into the game.
This confusion confines HoI4 and Paradox to a non-top tier position in the international game development game.
Given that the largest market for HoI4 is in English speaking countries, Paradox's CEO, Fredrik Wester, would do well to up his game...
and hire an English language editor.
(don't get me wrong...I very much enjoy Paradox games and respect the HoI4's development team's ability to publish a product to the international gaming market. But there are deficits in Paradox's ability to clearly transmit information. This post about "air-support, mission efficiency, and ground support" is one of several examples of information being "lost in translation")