Jon,
Much of what you say is true but I have a feeling we are going to have to agree to disagree on a few things and I don't want ruin a good thread so I'll try to be brief.
The soil profile doesn't have to be permanently saturated for water to run across the surface, you just need more water trying to get into the soil than the soil has capacity to move through it's profile at any one time. When it rains on most soil this happens.
What I refer to as 'surface drainage' isn't just water moving across the surface but the idea of trying to remove water from the surface as quickly as possible. Reducing the distance for water to travel to find the nearest drain is more effective at this than deeper drains. They are shallower (600mm minimum for fairways, 500mm min for greens is common) as at smaller spacing they don't need to be as deep to have the same effect that the deeper drains have on the overall water table and it saves abit of money. You get the effect of the deeper drains with added effect of removing the water quickly. Yes it is more expensive but there are added benefits. Deeper drains that then need to be added to in order to catch particular areas can end up costing as much if repeat work is required and awkward spurs and lines are needed.
But again it's 'horses for courses', every site is different.
The idea that they are "designed to fail" is pretty ridiculous. The stone will last just as long in a shallow drain as a deeper drain but as you clearly know all drainage is only as good as it's maintenance. If there is too much compaction and the water can't get to them that's when they will fail.
You probably know all of this but for those that don't this article is a good basic guide;
https://www.pitchcare.com/magazine/land-drainage-soil-water-and.htmlRight back to Woking....