My understanding may be a little different than y'alls because I'm in Texas, but our high clay soils are mainly Montmorillonite and other 2:1 clays. The surface area of these types of clays have a large surface area that allows for a lot of water to be absorbed into the pores. That's why you see the extreme cracks during drought conditions- when at field capacity, the clay swells immensely, but shrinks considerably when low in water content.
Even though the soil particles form larger colloids, there is still a pretty big amount of empty space in between the particles. In my soil class, it was explained like this- even though the clay particles are larger, and create large colloids, they can be thought of as a bunch of loose cinder blocks randomly piled up. Even though the area it takes up is big, there is a ton of empty space. On the other hand, soils with smaller particles (sand and silt) are like a bunch of bricks in a pile- it may take up a smaller overall area, but the empty space between the particles is not that big.
These clay colloids, whether they be platy, columnar, or others, hold lots of water and allow better percolation because of the "randomness" of the particles, whereas a structureless soil may be more tightly packed similar to a stacked cinder block wall.
However, compaction from increased traffic or other reasons can lead to less infiltration and percolation because the clay compacts easily. There is a reason that golf course superintendents are deep-tine aerating after a heavy topdress on their greens- to introduce some sand or organic material into the soil profile to loosen up the soil.
Forgive me if I'm way off base- I'm still trudging though graduate school and learning new things every day!