This is a bunch of nonsense, "engagement" doesn't matter AT ALL in a traditional sales model. If somebody buys your game, you have their money, it doesn't matter if they play it or not, they can even throw it in the trash and you still have their money. Even for a subscription service model, you get the subsciber's money every month whether they download and play games or not, so again "engagement" doesn't matter too much although you want to make sure they stay subscribed obviously.
There's two possible reasons I see why these platform holders think engagement is important. The first is because they foresee a grim future for console gaming where people, especially young people, would rather be on their phones than play console games. And in a world where social media is becoming more and more important, companies feel like they need engagement to generate social media buzz that can potentially amplify sales. Helldivers 2 comes to mind in that regard. The game generated a lot of buzz on social media, word of mouth if you will.
The second reason is because they're seeking alternate revenue streams such as in-game advertisements and product placements, and those can only generate revenue if the player plays through the game and sees that ad or product.
Either way, the shift of focus towards "engagement" doesn't forebode anything good for traditional gamers.