Usually a state machine is used for locomotion, legs moving, and the AnimGraph used to introduced slot nodes and branch points as torso blends. The state machine can only, as far as I know, play whats called absolute animation and is why playing one will reset the other. The AnimGraph can play Additive animation, a Montage or blend space, using layered blend per bone. The flow direction then would be.
Locomotion > AnimGraph > Blend per bone > output state.
An example using punching instead of say reaching.
if it helps here is what my current AnimGraph looks like.
