So there's some speed at which you can run for a long time. You can run faster than that for a short period, but you can't keep it up; it's not sustainable. Running faster than that is called a "sprint". Sprinting doesn't refer to a particular way of running, or a particular speed; what it means is exactly keeping a pace that is not sustainable for the long term.
So suppose a marathon coach and said
"The secret of running a marathon fast is realizing that sprinting is faster than running. So for the first 100 yards of the marathon, you should sprint. Then for the next 100 yards, you should sprint again. And then another sprint, and another, until you've run the whole marathon fast".
I would conclude they have no idea what they are talking about, and I would discount not only their advice on sprinting, but all their advice on how to go about running a marathon.