Yea, and drip all over your head down below even when it is not raining. Unless it is a modern teak that was just glued down. It is not if old teak decks will leak, but when. You end up with a nice wet core and it leaks all the time.
Exactly. Those old teak decks look nice enough, but if screwed down (which they nearly always were in the 80's) are a disaster. Most boats with a deck of that vintage have been scrubbed or sanded down so much that most of the plugs are gone and there isn't enough material to reseat the screws and install new plugs. If not properly secured, the deck will squeak as you walk on it, which to me is disconcerting. There is a nice Baba 40 in our marina whose owner removed the teak deck, filled the holes, and painted the deck with non-skid. Very nice job, the boat is far better for it.
Not exactly. A teak deck shouldn't have any finish on it. Gray weathering is safest. Any finish is prone to making the surface slippery.