Explain the software engineering behind this then. If you can’t explain it in basic terms, you don’t understand it yourself.
Everyone knows that helltide chests determine item rarity first, then another roll within that rarity to determine that it drops. The fact that everyone knew this and they added unique rarity to helltide chests in the patch, people may have just assumed that blizz were adding another method of target farming and making the uber uniques actually somewhat obtainable, instead of having to win the lottery to get them. It’s such a stupid mistake to add this functionality, that people assumed that it wasn’t a mistake.