That would depend on if you did purchase 19 or if you rented it through a membership option. If you bought it in the past, they probably just want you to buy it over again with the newer Platinum Edition.
Same here, that only happens if you subscribe. Stop subscribing and it reverts to normal without the plus, however this is a new purchase so unlikely to have bought and rented at the same time!
I have 105096 which was from the original bought normal game and 105100 which was the subscription plus version I downloaded, both now have plus however 105096 does not have the Content Store button.