That is not the commonly accepted definition of "efficient" in English. It would be more like "making good, thorough, or careful use of resources; not consuming extra."
The distinction is important because one can be very efficient (using resources carefully) while being ineffective (not achieving desired results).
In this context, the distinction is relevant because it is not clear that mass surveillance is a useful tool for preventing unlawful behavior (what most of us consider to be the desired result of law enforcement). Mass surveillance is effective at mass population control (e.g., subverting opposition political movements).
