I have recently started seeing it in my accounts in Credit Karma. It
shows all of the utilization under my name. I was expecting it to show
under my wife's account. Is this correct or is this a quirk with
Many people add an authorized user to their account (for example a child or a parent) to improve the credit history of the new user. When they add an authorized user the data from the card is then added to all authorized users credit file.
Many people see this feature you noticed as a good thing. It allows somebody that has a thin file to benefit from an account that has a higher credit limit (helping their utilization numbers) and may also help their average age of their credit lines. Of course if the new user goes crazy with the card, and is slow to pay their portion then the score may be dinged or even severely impacted.
It isn't a problem with Credit Karma, because they can only use the data they are given. Unless the credit card company said that person X charged this amount then they can only use the amount and limit of the entire card.