Should garment ease be proportionate to size?

When I learned crochet, I crocheted few garments using the patterns available online. Most of the patterns had constant ease for each size. Then I thought that the ease shlould be proportionate to the size. I found few articles online mentioning the same. But I was not sure whether adding proportionate ease would give same fit for all the sizes and wanted to calculate it mathematically. I wanted a proof. So I did some calculations, and to my surprise the old method of adding same ease would give you the same fit for all the sizes and not the proportionate ease. If you use proportionate ease like 15% or 20% of the chest circumference, then the baby sizes clothes will be tight and the larger sizes clothes will be too loose. I would try to explain this with a diagram. (I have just calculated it theoretically). 

It would be great if any crochet or knitting designer try this concept and then confirm it practically. It would be really helpful for all the crocheters and knitters.

If R1 is radius of a body and R2 is radius of a cardigan, then for similar fiting garments, we want (R2 - R1) to be constant. It is the measure of how the cardigan will fit around the body. And to get constant (R2 - R1) we have to add constant ease, lets say 4" to all the sizes. If we add proportionate ease eg. 15% of the actual body measurement, then it will vary with the size and (R2 - R1) won't be constant. To confirm this theory, I did few calculations. I used newborn to 5XL size measurements to confirm my theory. (I will upload the calculation pictures shortly if anyone want to know in detail). I used circumference measurements to calculate the radiuses, and then drew the circles using radius measurements.

For red cardigan, I added proportionate ease (20% of the body measurements). For blue one, I added constant ease i.e. 4". 

As you can see in this image, when you use proportionate ease, the fiting is different for different sizes.

But when constant ease is added, fiting is exactly same for all the sizes. Hence it is confirmed that no matter what size garment you are making, the ease should be constant for similar fiting.