[kragen]

Yes, I think that's a perfectly reasonable way to describe the amount of rope produced in South Africa. It uses the correct units and therefore contains no ambiguity. Saying instead that the total amount of rope produced in South Africa was 16 billion meters, leaving the "per year" implied, would, by contrast, be ambiguous and open to misinterpretation; equally plausible interpretations would be "in all of history" (the literal interpretation) or "per month". Unless, as in this case, the statement was qualified with a particular year-long time period, such as "in 2019", in which case "500 meters per second" or "16 billion meters" would be equally unambiguous ways of describing the situation.

"500 meters per second" is not just (total production per year) / (seconds in a year) but also (total production in a day) / (seconds in a day) and (total production in a month) / (seconds in a month).

Meters per second, like watts, has the advantage of being an SI unit and therefore facilitating calculations with other SI units without requiring a bunch of numerical conversion factors.