Interesting! It is excellent to know that there is, according to Susan Huxley, a difference. I’d always known that stitch to be called a 5 thread safety stitch, which my machine can’t do as it’s only got 4 threads.
I generally call what I have a serger and what I do with it, serging. That is, unless I’m talking about the specific stitch I’m using, such as 4 thread overlock, or 3 thread overlock, or rolled hem. Yes, I’m in the US.