Perhaps, if there have been material events that change before the 20 day window, then another amendment must be written. This could go on for a while at the rate Neom is going.
If, a "Fortune 100" is negotiating a stake, imagine what they would expect to get out of the way and clarify before moving forward. I would be concerned about litigation, dilution, and acquisitions being cleaned up to meet with my approval. This certainly would explain the delays and the Quiet Period. I tend to believe that the quiet period is either self imposed or due to critical NDA's.
I am not suggesting that such events are taking place.