For some reason I have trouble making sense of their diagrams or photos - they seem very blurry and I didn't figure out how they show "where the water is". But I agree with the text.
As long as I just "take it on faith" that the boundary where a fine-textured layer sits on top of a coarse-textured layer is practically an IMPERVIOUS layer until the surface layers are "saturated" and water HAS TO come out the bottom when more comes in the top, I can agree with whatever articles ay about perched payers.
But why is that?
I understand that capillarity is stronger than gravity in soil. If there is no capillary connection between (say) a layer of peat moss sitting on top of gravel, and the gravel under it, the only force acting to pull water out of the peat is "mere gravity" and the capillary attraction of close-packed peat fibers trumps gravity by a large amount.
Again, WHY is there no capillary connection?
Today my best answer is: "capillarity comes from small things spaced closely together. With gravel, the ONLY capillary sites are where one grain touches another grain - like 3-4 POINTS of contact per grain of gravel". Be generous and say there are 1-2 grains of gravel in every cubic centimeter. Phooey, that's only 6-8 POINTS of contact per cc!
A cubic cm of peat must have hundreds if not thousands of fine fibers, each touching the other for their entire length.
In this way of looking at it, water in the peat layer is pulled HARD into thousands of times as many capillary crevices in each cc of peat, as in gravel. Maybe tens or hundreds of thousands times more capillary area. And in peat, every capillary layer is in intimate contact with other capillary layers, and water can be pulled from one to the next, continuously through the whole mass of peat.
And what happens to a brave water molecule that manages to escape from the peat into the gravel? It would just sit on whatever gravel grain it reached, finding no capillary path to move along. Then the water would stop moving into the gravel.
Or, one in ten or one in a hundred brave water molecules might reach a grain of gravel right NEAR a point where that grain touches one other grain! Big whoop, that one lucky water molecule might transfer to the NEXT grain of gravel by capillary attraction. It would stop there.
So whether or not there is any "connection" from the peat layer into the gravel layer, there just plain ain't no CAPILLARY PATHS in gravel!
The only way water can move through gravel or even INTO gravel is to become SATURATED enough in the upper layers that bulk amounts of water are FORCED out of the peat's capillary embrace and into the gaps between grains of gravel.
Where gravity is strong enough to make it flow downhill (between grains, due to gravity - not through capillary paths due to strong capillary forces.
Now that the water has escaped from capillary forces and is IN the gravel layer, there are almost no capillary sites except for the few points of actual contact between one grain and its neighbor. Those sites might hold a tiny amount of capillary water, but they are not connected, so there is no capillary flow.
Only when there is enough water in the gravel to saturate all the capillary sites can water move through gravel. The "free", excess water has no capillary forces, so it can just drop like a rock under the (weak) force of gravity.
I don't know if that's an accurate way of looking at it, but it lets me get to sleep at night!
If it sounds weird that capillarity is stronger than gravity, consider a capillary tube of glass. The ID of that tube is WAY larger than 30-75 microns! Despite that, the tiny "collar" where the water meets the glass lets the water feel the capillary attraction of the glass. That force is enough to lift ALL the water in that tube several mm, against gravity! The tiny capillary fringe around the circumference of the tube, plus surface tension, HAULS that heavy water up MULTIPLE millimeters, against the force of gravity! Like a flea hauling a dog on a leash. To moe the dog at all, it has to be one STRONG flea.
Now imagine the same effect in the soil, running through micropores and mesopores only a few tens of microns in diameter (a couple hundredths of a millimeter - say, room for several bacteria to wander in without being very crowded). Down there, it isn't 30 microns of capillary fringe hauling a huge mm-sized column of water, it's just 30 microns of capillary film hauling on 30 microns of water! Of course it's much stronger than gravity.