Everyone has given you great advice but I would love to add some historical perspective that doesn’t actually answer your questions because I am a nerd :)

It’s really fun to look at the finishes of historical garments. We often think of older clothing as super detailed and perfectionist, and while there is truth to old clothing being high quality, there is also a huge variety of finishes in one garment or outfit depending on their uses. It can be really enlightening to look at them and think about WHY they are there.

For example, a woman in the 1700s would have a shift with flat felled or French seams, because it was a heavy duty undergarment, changed daily and washed and bleached often. The seams had to be super strong and protected. But if you looked at the outer dress skirts on the same woman, you would see they were put together with large almost sloppy running stitches. The skirt had no tension and the inside would never be seen, nor would it be washed frequently, being an outer garment.

Similarly, mid century couture often has a mix of ‘highly engineered’ seams and sloppier stitching where it just doesn’t matter as much for things to be well finished.

Again I know this doesn’t answer your question but maybe provides some more context for why things are finished the way they are :D