"While there was only one major acquisition announced during Xbox's E3 2019 press conference, Microsoft has one more new studio up its sleeve. In a blog post shared after the show, Microsoft snuck in that it has created a brand new studio for Age of Empires headed by Microsoft veteran Shannon Loftis. The news follows last night's announcement of Age of Empires II: Definitive Edition, which updates the classic strategy game with 4K visuals and a brand new campaign, The Last Khans. It will launch this autumn."
So that's 15 studios under XGS. It's weird they did not announce it during their show but instead announced it through a blog post.