Hello,
I can understand how frustrating this issue can be since both the Chest and Gem names were incorrect in that case. This problem was reported to our services as the Customer Support agent mentioned to you. After further investigation, it turns out to be solely a description/name issue both for the Box and the Garnet > Peridot. Initially the box was named Gilded Square Gem Chest instead of Gilded Triangular Gem Chest. Likewise for all of its content which was named [Gilded Square X] instead of [Gilded Triangular X] and on top of that, "Garnet" was present instead of "Peridot". So it's basically 2 localisation issues on a single box hence why I understand why this could have been extremely confusing for you.
However when it comes to the item itself (on the back end) you received the proper reward, only the description/text is incorrect that is why the Support Team did not replace your item since from a functionality point of view everything worked as it should (the box is supposed to give Gilded Triangular Gems, you got a Gilded Triangular Gem.)
Would you be able to name the players who claim to have received Square Gems from that very box and when so we could investigate further and confirm what exactly happened there? Are they really certain that they obtained an actual Square Gem and not just a triangular one with a wrong description/name? Because the box should never have given any Squared Gems. Thanks again!