This seems like a complete non-issue. "18 karat" isn't a measure of gold by volume, nobody buys gold by volume, and this "Apple gold" has the same amount of gold by weight as any other 18k gold.
Not really - unless you are wealthy enough to ignore the price when buying jewellery, you are buying by weight. Except for the high end jewellery, the price has a direct relationship with weight in gold, not the volume of the piece.