A Stadia Pro subscription nets you both "free" games and discounts on games you purchase and, like PS Plus and other subscription services, you lose access to the games you got through the subscription. Today, however, there have also been reports that you lose all your discounted games, too. It's nonsense.
The source of the confusion is a tweet from Google Italy that states "games obtained free or with discounts thanks to the Stadia Pro subscription will no longer be available once the subscription has expired." It's absurd, of course, but straight from the horse's mouth. Fortunately, that horse was off its game today, because it's apparently not true.
Google has since clarified both on Twitter and in a statement that purchased games, including ones with discounts, will remain even once the subscription ends, just as you'd expect. To get access to free games you've claimed, however, you'll still need to resubscribe.
Hi! To clarify, free games claimed with your Pro subscription will not be accessible if your subscription expires. Any games you purchased with or without discounts are yours to play even if your Pro subscription expires.November 21, 2019
As you were, then. And If you're on the fence about getting on the streaming wagon, check out our Stadia impressions so far.