This in the CNN feed in the last hour :
The Joint Maritime Information Center (JMIC), which is overseen by the US Navy, raised the threat level in the strait to “substantial” on Saturday, a step it said it took following attacks on merchant vessels.
Meanwhile, a route through the Strait of Hormuz near Oman has been expanded to allow for greater passage of marine traffic in both directions, the JMIC said, suggesting the US is pushing back at Iran’s control over the waterway.
So there we go. The MOU says Iran is to do it, but the US ain't doing that. They are doing their own thing.
So what was the point of the MOU ?
I suspect the ship that was hit while apparently not following the rules was doing as instructed by someone with alternative rules.