Thanks for the observations and reasons for doing this, I would add another.
My main aim is to keep soil fed and mulched, so if the soil between rows of leeks had no organic matter on the surface by late autumn, I would spread compost (which might be old horse manure) between the rows.
My aim is not to feed the plants, but to feed soil organisms.
The result is good also for softening the surface and making it easier to pull leeks in freezing weather. Then after harvests and coming into spring, the ground is ready for a new sowing or planting, without having to rush to do that in spring.
So it’s also time management. Everything interlocks in a pleasing way.
