It is interesting that my comment got both upvoted and downvoted. I didn't know that people on hacker news knew that much about sewing!
I will just say what I thought was too technical to say. I have actually sewn sleeves and have done pattern matching between the body and the sleeve.
Two things impact the pattern matching.
Most of the ease is in the top of the sleeve cap and not in the body of the sleeve cap. The first thing I do is make sure the pattern is as far away from the sleeve cap as possible. Then I check if I can fool the eye. If you look closely at the plaid closest to the top it is shifted slightly which was disguised by matching the vertical stripe instead. The maker of the coat did both of these things. So - nothing was proved since this is normal sewing practice.
The second thing that impacts pattern matching is the stretchiness of the fabric. Pattern matching in knits is very easy even with ease. I don't think this was used in the particular coat.
I am very surprised that the author thought that a photo from an unknown manufacturer proves that easing was not needed. They could have easily proved it by sewing something. This leads me to believe they don't know as much about sewing as they implied.
Some of my background: I am a retired software engineer. The first half of my career was in 2d and 3d graphics rendering. My mother taught sewing professionally with a home economics degree from UC Berkeley (back when they had such a degree). She taught me as a child how to pattern match plaid. I have been fascinated by the math of sewing - but only as a hobby.
I will just say what I thought was too technical to say. I have actually sewn sleeves and have done pattern matching between the body and the sleeve.
Two things impact the pattern matching.
Most of the ease is in the top of the sleeve cap and not in the body of the sleeve cap. The first thing I do is make sure the pattern is as far away from the sleeve cap as possible. Then I check if I can fool the eye. If you look closely at the plaid closest to the top it is shifted slightly which was disguised by matching the vertical stripe instead. The maker of the coat did both of these things. So - nothing was proved since this is normal sewing practice.
The second thing that impacts pattern matching is the stretchiness of the fabric. Pattern matching in knits is very easy even with ease. I don't think this was used in the particular coat.
I am very surprised that the author thought that a photo from an unknown manufacturer proves that easing was not needed. They could have easily proved it by sewing something. This leads me to believe they don't know as much about sewing as they implied.
Some of my background: I am a retired software engineer. The first half of my career was in 2d and 3d graphics rendering. My mother taught sewing professionally with a home economics degree from UC Berkeley (back when they had such a degree). She taught me as a child how to pattern match plaid. I have been fascinated by the math of sewing - but only as a hobby.