"Are grout and cement slurry the same thing?"

In the case of grout, the suspensions and solutions used for grout injection are also considered grout.

Water glass and CB injection are also types of grout.

In other words, it refers to a fluid that is injected to fill cavities, voids, gaps, and the like. (wiki)

That would be what’s known as “cement milk.”

By the way, cement slurry is a mixture of cement and water.