That's a good article in the OP. If there are contradicting observations to the sinking ship effect it is the duty of that scientist to get to the bottom of it, not to ignore it and continue repeating the dogma.
You can "get to the bottom of it" by observing ships, islands, wind turbines, and other items on the water which are far closer than the point at which they appear to "sink".
Apply the principles of Experiment 2, and use observer height vs. object height to determine whether or not your line of sight is parallel to the water.
Like this;
If, as in experiment 2, Rowbottom had a middle (black) flag which was half the height of the (white) others around it along his line of sight, then, if he looked along the tops of the flags along line A-B, or at the top of the higher flag at D, his sight line would
always be above the height of the middle black flag, wouldn't it? There's no way to draw a straightline A-B or A-D which meets the black flag at any point.
So, if you, as a zetetic observer, were to look out from height H, across an expanse of water far longer than his canal, at an island, hill, or other landmass of similar or greater height than your observation height, then all objects of lesser height than H between you and that far landmass would be below your sightline. Their highest point could not get inbetween your eye and the far landmass. If the expanse of water is truly flat.
Agree?