Rotational gravitation has never been experimentally confirmed. It is pure speculation.
Watch the pendulum as it swings. It will rotate in the direction of the stars overhead.
That's a direct cause and effect.
But not at the same rate. And this is the important bit. A Focult pendulum would work on a flat Earth if the Earth was rotating. You would get a rotation of the pendulum.
BUTOn that Flat Earth, no matter where your position on the Earth was, the pendulum would rotate at the same rate.
However, a Focult pendulum on a Round Earth would have different rotational periods depending on your location on the Earth.
A Pendulum on one of the RE Poles would rotate once every 24 hours. A pendulum on the RE Equator would not rotate at all.
If you are correct and it is the Heavens that are causing the Pendulum to rotate, then it too would exhibit a constant rotation rate regardless of your position on the Earth.
The problem is that you are ignoring evidence (against the express statement by Rowbotham in ENaG -page 1 - to include all the evidence) where by (even unpowered) Focult Pendulums have a variable rotation rate depending on their position on the Earth.
Also, you don't need to have the pendulum rotate for a full day to measure the rate of rotation. An hour would be sufficient to make accurate enough measurements. You can increase the time a pendulum would swing by increasing the weight of the pendulum.
Also, would you accept it if a FEer built a Focult Pendulum and used a magnetic driver to keep it swinging? Then you could be assured that there was not conspiracy adding in devices that would cause the pendulum to rotate.