I don't see any MFS spec in the OP's 1000 yard swim ... I took it to mean exactly what it says ... swim. 1000 yards with mask, fins & snorkel isn't that difficult. However, I still don't see how that helps someone be a better scuba diver unless you're diving someplace where you're going to be anticipating having to go a half-mile or against a heavy current in order to get out of the water.
FWIW - NAUI's instructor watermanship test required a 450 yard swim and 800 yards with MFS when I took it in 2004. That's reasonable for an instructor. For entry-level, I found the YMCA's requirements of a 300 yard surface swim, 50 foot underwater swim and 15 minute survival swim to be reasonable and adequate to judge someone's fitness to dive.
... Bob (Grateful Diver)
FWIW, I recall swimming 800 yards with no gear for the PADI DM course in 2-3 foot swells. One would expect a DM or instructor to be able to make a long swim. But, I think there is also value for any diver to have the fitness and the skills to make a long surface swim. Maybe the average resort boat diver doesn't need much more energy than to walk to the back of the boat, but a lot of shore divers routinely make long swims.