When shipping the buckets they get vibrated a lot. What ends up happening is the separation of different sized particles and even elements. You then get inconsistent/odd measurements in your salt after mixing. There can be random pockets whith parameters out of wack.
Ever hear of someone complaining about a 'bad batch'? 90% of the time they either mixed improperly, or used the top layer of salt without shaking the bucket, got bad readings, and started flaming bad batch. The top layer is notorious for bogus readings.
Although if you use the whole 200g you would have good parameters, if you only used the top layer you would likely have odd parameters. The rest of the salt would be odd on the opposite side to compensate for the top.
Many people pour it from one bucket to another to mix it. Or if it comes in a bag pour the bag into the bucket. Personally if i have a bag, i dump into bucket. If no bag, i just give it a good shaking.
This has nothing to do with how good/expensive a salt it. It happens to all salts.