Help Me Choose Timber Nation Rack-- All Wood or Threaded Rod?

Hard to take seriously a company that advertises a block of wood as isolation. A metal rod is going to resonate at higher frequencies than a wood one, so transmissability is going to be higher for more lower frequencies for metal than wood. But I can not see any real isolation method in this device at all, which may or may not have anything to do with any of the OP’s goals. Its just going to be a difference in resonance profiles that may add up to something or not. Maybe just get the one that looks best.

My post has nothing to do with maple, but I do have a Finite Elemente rack.

Vibration isolation is preventing vibration transmission from one source to another, which wood itself does not do. There are different methods, but the one used in all racking systems I know employ a low pass filter. These can be made different ways, but they all resonate at a low frequency, above which vibration transmission becomes progressively inefficient.  Examples include vibraplane, minusk and thorlabs. You can look at a transmissibility curves yourself.  This not to say isolation is always the goal. I don't know your goals.

The wood rack, like all racks is going to resonate at particular frequencies depending on mass, "stiffness", damping and dimensions. You may like it the way it sounds; I don't know. What I know is that is does not isolate, although may be you or falconquest can counter with physics-type reason if I am wrong. Actually I think if it is placed on wood flooring, the acoustic impedance is going to be small vibration will efficiently transfer both ways with little reflection. I hope you enjoy the sound of your rack. They make a big difference.