ELI5: Automotive oil weight ratings.

This has long perplexed me and I will attempt to explain why.

At 100F a 20 weight will flow better than a 30 weight which will flow better than a 40 weight. So, the higher the number, the less easily it flows. Now the "W" weights indicate the viscosity of the oil at 32F (or 0F I forget which temperature) and at 32F a 0W flows better than a 5W which flows better than a 10W. So again, like above, the higher the number, the less easily it flows. I get and understand all this but a 10W-30 flows with a 10weight viscosity at 32F and as it warms up it flows with a 30 weight viscosity. The number goes up, so the oil flows less easily but with the above stated logic and the fact that we all know if I drain 10w30 oil in a car that has sat over night in the winter verses draining it after it just got off the interstate after a 100 mile drive, the hotter and higher 30 weight oil flows better and faster out of the oil pan than the colder thinner 10W weight oil... It's this that has me confused. In my head oils should be like 50w-20 or 75w-30 because the cold oil clearly flows slower than the hot oil. The colder thicker oil flows like a 50 weight when cold and as it warms up it flows better like a 20 weight and so on....this is where my brain is hung up. Can someone help explain this.