I've always heard (and read) that to develop aerobic capacity, frequent stops are bad. Continuous runs are supposedly what provide the stimulus to develop capillaries, mitochondria etc. But, Igloi's proteges didn't even do much medium distance without resting, right? It was lots and lots of 100's-200's. Didn't one of Igloi's marathoners (forgot his name) do tons of 100m at 18-20 seconds? He later ran a marathon around that pace. Obviously, he must have developed decent endurance. Schul must have had decent aerobic development to medal in 64. That's not just untrained talent.
So perhaps the stuff most people are being fed about how and why distance training works on a physiological level needs to be tweaked? Fatiguing a muscle long enough or OFTEN enough in a space of time may be the deciding factor NOT whether you run continuously or rest a bit during bouts.
Running continuously may be more efficient. Compared to doing 90 minutes of continuous running, you may need 2 hours of short intervals to fatigue the muscle the same amount. Of course, you may be able to run slightly faster speeds with the intervals, thereby exercising more of the same muscles used at race pace.
I am by no means an expert on this, which is why I phrase all this as conjecture. Anyone have an answer?