It may be due to the "coating", which ensures child safety. You can read about it in various forums.
Just in case someone is also considering buying these batteries: there could be problems with this product.
I think so too (especially because of the price), the only strange thing is the weight. A single battery weighs 3g, including packaging 25g ^, so one of the 3 specifications is wrong. If it was just one battery, I'd just return the item if I were you.