https://www.gamespot.com/articles/say-goodbye-to-these-xbox-one-games-pass-games-on-/1100-6458907/

If you're an avid user of Xbox One's games streaming service Xbox Games Pass, get ready to say goodbye to a significant amount of 360 titles. On May 31, 21 titles are leaving the service's catalog.

Out of the 21 titles on the way out, one two are Xbox One titles, and the rest are from 360. We're not sure why these titles in particular are leaving the service, but we do know that third-party titles aren't permanent additions--though this cut is probably the largest the service has seen so far. Some bigger titles on the chopping block are Bioshock, Bioshock 2, and Bioshock Infinite, as well as Borderlands.