The developer is Turtle Rock Studio, and Valve is the publisher. So it looks to be an excellent collaboration, a talented studio under the aegis of the high quality veteran game company most famous for the Half-Life franchise.
I bet that the actual development team at Valve is working on the next Half-Life 2 episode, and possibly conceiving the next Half-Life game.
Valve is simply being just....well, Valve, as you stated! LOL!
