Why New Look dresses tend to fit so much better on full bust?

I got the answer from Russian sewing forum. The reason is that authentic New Look patterns were totally different from what we have nowadays. Fit was much tighter and allowance distribution was different.
By modern standard of pattern-making 4.5cm (1.8″) allowance in the bust should be distributed like 1-2,5-1 (front-armhole-back), by New Look standard it’s more like 3-1-0,5. But in most cases it’s more than 4.5cm in modern garments. But due to different allowance distribution with New Look we still have more room in the bust for the same size!
And there is one more drastic difference: New Look dresses have no allowance in the waist. They also have higher armholes and totally different construction of sleeves to allow hand movements. Modern designers usually solve hand movements task by adding large waist allowance (up to 7cm or ~2.8″ for basic pattern, real garment can have much looser fit), so when you put hands up all garment moves up, that would be impossible with tighter fit. So in addition to more room in the bust in New Look dresses we have much smaller waist!
So measurements of typical New Look dress more close to Pepperberry Really Curvy or BiuBiu BB than to modern high street, despite the fact that it was designed for an average bust and bust-waist ratio.