Decided to order the black ones this time just to see if there difference is based on color. They have have two different production areas producing the colors separately and no exactly the same which is why we have variance going on. Or just could be a rework thing based upon some date where they change production of the units completely.
Production variations for a product are true for every industry. While it would be nice if they were communicated to consumers, companies are in no particular obligation to do so. I appreciate when people dig into production variations and document them.
Japanese camera and lens makers used to make all their gear in Japan, but most have moved production to Thailand, Vietnam, and in some cases China. Audio Technica used to make their headphones in Japan, but have moved production to other places. AKG used to make their headphones in Austria and Germany, but now they're made in China, their headquarters in Austria was shut down last year, and they are just a division of the South Korean giant Samsung now.
What I think most people don't understand about brands and products though and why some products cost more than others is that it isn't just about the design, materials, location of production, or even performance. A big part of cost is (or should be) about quality assurance and how consistent products are - or at least how responsive a manufacturer is to inconsistencies in a product when reported by a consumer. Modern products can have a lot of variation. Here is a really good example:
https://www.lensrentals.com/blog/2011/10/notes-on-lens-and-camera-variation/
"We know from experience that if we mount multiple copies of a given lens on one camera, each one is a bit different. One lens may front focus a bit, another back focus. One may seem a bit sharper close up, another is a bit sharper at infinity. But most are perfectly acceptable (meaning the variation between different copies is a lot smaller than the variation you’re likely to detect in a print). I can tell you that, but showing you is more effective."
Note that all that data comes from Canon L prime lenses. One of the reasons lenses like a Zeiss Otus cost more is quality assurance and reduced lens-to-lens variation (along with everything else unique about their products). By that same token, that is part of what makes (or should make) an expensive headphone expensive - better matching of internal parts when there are pairs/multiples, better materials, better tolerances, more consistent performance coming off the bench all the way to the consumers' hands. When there are changes to places of manufacture, the knowledge and experience of what made the product great in one place is transferred to the new place so it doesn't have to start the quality assurance learning process all over again to make a great product.
The reality is that if a product is high performance but inexpensive, any consumer is likely rolling the dice. Good quality assurance and a consistent quality product will always cost time and money. When I read a review of any product, if the person reviewing it is reviewing just one copy of that product, then all I can take away from that review is what that one particular copy of a product is like (with enough reviews from enough reliable sources, I can correlate sufficient information to start to be able to feel like I can reliably infer more general performance). When a reviewer is provided a review copy of a product from a manufacturer, I factor that in because that inherently makes the review less reliable as something that can represent the average experience because that review copy could very well be cherry picked by the manufacturer (basically that reviewer could be experiencing a higher level of quality assurance in what they receive vs. the average consumer).
So, with all things, consume them with an appropriately sized grain of salt.