That's mind bending, never thought of gravity that way (being a force like EM, and subject to a propagation speed).
In my mind, gravity was just some sort of "vacuum" the mass leaves as it moves, and other bodies get "pulled in" because that's the space where the "energy" (mass) levels are smaller, and the system tends to a stable state. But not something like a wave that propagates, just a side effect of the global system, not tied to speed in any way.
Actually, the "gravity" that propagates at the speed of light isn't really a "force"; it's more like changes in a force. A completely static gravity field doesn't have to "propagate" at all, because it never changes; but it can still produce a "force" (i.e., it can still cause objects to freely fall towards the source).
In my mind, gravity was just some sort of "vacuum" the mass leaves as it moves, and other bodies get "pulled in" because that's the space where the "energy" (mass) levels are smaller, and the system tends to a stable state. But not something like a wave that propagates, just a side effect of the global system, not tied to speed in any way.