I agree with you. But to clarify, the outer Eta layer does not chip off, but it is quite soft and can wear off pretty quickly under the right conditions. For example, if anchored in a seabed with sand or with sand particles in the seabed, and you get a pretty rocky sea state that is making the chain work a fair bit, the combination of the contact stress and the abrasive seabed could cause the Eta layer to abrade away in a few hours. The reason hot dipped galvanized is used in anchor chains is because of the lower levels that are quite hard and abrasion resistant. No other galvanizing process produces this metallurgical structure. Well, there is a new process being done by an Israeli company that claims it does, I've only examined it superficially so can't really say if it truly is an adequate substitute.Even when wet, our chain has a dull, flat appearance. Not suggesting Defender did a substitution, just my observation and experience. If it were me, I might have an industrial chain expert weigh in. And I've never experienced quality produced hot dipped galvanize material actually chipping off. I suppose, too, that the production process itself can result in different quality grades.
There are some differences in production processes - particularly in how the chain gets treated after the hot-dipped bath. There are coatings that can be used that help stabilize the Eta layer. It wouldn't surprise me in the least if these kinds of steps get changed through the wonderful "value engineering" departments that float through manufacturing processes... These treatments tend to be highly proprietary in nature with almost no publicly accessible information nor documentation to know if they were used or not by a particular manufacturer.
Anyway, this is a sailing forum and not a metallurgy forum. I've probably already taken up way too much bandwidth on this...
dj