watchesplayer,
I'm not a watchmaker or materials engineer but please let me make an observation as an ordinary enthusiast.
You have found out that handmade brushings and natural graining of steel produces variations that still satisfy Quality Control limits.
While your eye is drawn to the brighter lines that you circled, did you notice darker bands across that side of the watch?
There are at least four bands to my eyes that counterpoint the lighter band you found.
It all averages out, I guess. Some people notice lighter bands and others see darker bands. You can't chase them all.
As it is not a 'fault', it looks like Chopard service centre is doing more than normal to keep you happy. They can't replace every non faulty product.
Again, only you know the legal and usual consumer practice in HKG that applies where you live. Experiences from other regions do not apply.
The fact is that the best people to rebrush the case is the factory that knows best.
The big issue is that there is no guarantee about the final appearance because of the first statement above. Handmade brushings and natural graining of steel does whatever it does....it's your choice....brush again or just leave it as is.
Pesonal opinion.
I looked at my brushed cases from diferent brands and they have similar light and dark bands if I squint hard or use my imagination under different lighting conditions.
I didn't notice before.
Just use your watch and normal wear and dirt should change things...maybe new bands will appear elsewhere? Then, what will you do?
Regards,
MTF