Ultimately, I think this signals the slow death of Windows based handhelds. Despite the recent addition of Lenovo, ASUS, and MSI, smaller manufacturers have been making Windows handhelds for years.
You'd think that with the big boys stepping in, that would have prompted Nadella to do literally anything to improve Windows handhelds. Even something as basic as a launcher that sits on top of Windows (like Android) would have been helpful. Instead, many Windows handhelds still require attaching a physical keyboard during setup because there's no guarantee that the onscreen keyboard will work.
So I'm not surprised to see OEMs testing Steam because it provides a better user experience, and cheaper due to not having to license Windows. The second loser is Epic (and everyone else not named Steam) because now there's one less reason to buy games from another store.