Edit: By the way, it DOES matter what the particle size of your soil is- VERY MUCH- as any gardener or soil scientist will confirm.
One of the properties of water is that it will actually adhere to the edges of its container, rather than flowing entirely freely- even, to a certain extent, against gravity!
You may demonstrate this by putting a very narrow tube such as a hollow reed into a glass of water and noting that the water level within hte reed is higher than that within the glass. The relative difference between these is DIRECTLY correlated to the interior diameter of the tube, with narrower tubes allowing the interior water level to rise much higher- defying gravity! So drainage is quite impeded, if you follow the logic, by smaller interstitial spaces between soil particles.
Silty and clay soils have the smallest pore size, and drain the slowest. If you have ever grown a plant, you will know that you never use clay in your garden soil except in very specific instances, with very specific plants, that are few an far between. Perlite is designed to have a very chunky structure, with large interstitial spaces; hydroton, then, would be the extreme example of this. It holds far more oxygen than a dense soil would, and drains far more freely.
Peat moss STARTS with a fairly nice particle size, but over 6-10 weeks from first wetting, will break into smaller particles, which do not drain, and will suffocate your plants' roots.

But I guess that doesn't matter, which is why it does not appear in ANY grow videos.

The beauty of a forum is that you can freely move from topic to topic, choosing the order of learning that suits you best, and re-visit subjects of current interest without having to find the one spot on that one video that mentioned it in passing.