Let me have a try. The teak you see is like icing on a cake. The real deck is underneath, usually 2 layers of fibreglass, top and bottom, with some kind of wood in between, a kind of sandwich. Sometimes there is no bottom f/g layer.
The screws attaching the teak on top(see all those little plugs covering the screws?) conduct water below, = rot in the "sandwich". Teak applied on top these days is glued not screwed, so no intrusion.
If you remove the teak on top, repair the real deck below as necessary, fair the deck, fix all the screwholes, you add one or more layers of f/g on top to replace the teak, usually for stiffness. That`s probably what you are seeing.
2005 Integrity 386 "Sojourn"