Yes, throughput vs latency is a very important distinction. An airplane is always faster then a train, but if what you are measuring is throughput, a train can be more performant. It depends on the context, but that's fine. There is no such thing as a made-up word if the word has a meaning, and is regularly used by a group of people.

So is the GPU more or less 'performant?'

That's right - the CPU is faster at completing the job, though the GPU executes instructions more quickly.