I just took a second look at the pictures. There is definitely something going on there. You can see that there are a few bungs in place and maybe even tight. All the visible screws are neatly lined up across the width of the boat, especially at the front deck. This is very unusual. Since teak is so expensive most boat manufacturers use random length boards. If they can get 18 inches out of a board they wouldn't cut any off it to match the other boards, too wasteful. As a result of the random board lengths there will be a screw near the ends and the remaning length of the board will a screw every 4 or 6 or eight inches, different with each board.
That is not what I am seeing here. I think those screws have been added at a later time, not countersunk or "bunged". And to make it worse, they appear to be stainless. The original would be brass or bronze.
It could be that they were getting some "flex" and thought that adding screws would help. Or maybe the planks were popping loose from the rotten glass underneath and they needed to be screwed down using a more aggressive screw. Maybe even the heads were sanded of some of the original screws and the boards were getting loose.
Whatever is going on here ain't good. I think you need a moisture meter, an expert survey and I would probably still "take a walk"
pete