>Physics are always tied to framerate. There is not a game physics library in wide use that is independent of update rate. In practice what usually happens is that the physics library has an internal tick rate (say every 1ms or every 2ms) and every frame N physics ticks occur to catch up. Without this, the physics sim would be dangerously unstable (and in practice, it still is).
This is called a fixed timestep, and is not what people mean when they say "physics is tied to the framerate", referring to the rendering framerate and generally instead meaning that you pass the actual delta time elapsed between rendering frames into the physics simulation, which can cause bugs at extremely high or low framerates. I have no idea if FO4 works this way, but many engines do (even if it is usually a bad idea), so it's not completely outside the realm of possibility.
This is called a fixed timestep, and is not what people mean when they say "physics is tied to the framerate", referring to the rendering framerate and generally instead meaning that you pass the actual delta time elapsed between rendering frames into the physics simulation, which can cause bugs at extremely high or low framerates. I have no idea if FO4 works this way, but many engines do (even if it is usually a bad idea), so it's not completely outside the realm of possibility.