It's a bad word choice, but fitting it into an acronym is more important than giving good advice

Probably he was just fishing for adjectives, but generally, optimization just just the minimization of any function. Efficiency could be the minimization of a function describing resource usage.

In the real world, in real time systems one often optimizes for low jitter, which is often not contradictory to optimizing for efficiency, as one may reserve resources to keep them available in order to process requests faster, even though they're not required.