Yes, the ledge above provides shelter so the extra bamboo poles don't kena rain. Plus because the front door of another unit on the floor looks directly into my service yard, I've put up a canvas sheet to provide some privacy. That plus the orientation of my block prevents even heavy rain from coming in.
Because the canvas sheet covers just enough for privacy, there's still enough air circulation.
In any case, I think new BTOs no longer have such configurations. The design of BTOs has really improved. Mine was launched in 2008.
Re: security, I think the units on the lower floors have additional security devices like grills etc. Even my high floor has a grill protecting my service yard. It has lots of small holes instead of bars so there's nothing you can grip on to. In any case, because of the design, it's a huge risk to try to climb in. You would really need very, very pro equipment and skill to go from the corridor into the service yard.
Re: the drying rack raising and lowering mechanism, there is an internal locking device that regulates the movement. You first need to pull the rope back at an angle to unlock it. Then you can pull it up and down. Once you bring the rope back to vertical, the locking mechanism activates and holds the rack in place. The hook on the wall is meant for neatness (to store excess rope) and doesn't secure anything. I didn't install mine. I just bundled the excess rope up and tied a knot around it
Re: water heater, gas water heater confirm plus chop can go into service yard. Electric storage heaters are usually installed in the common toilet. There's existing plumbing and power (with switches at both toilets) in one of the ceiling corners usually.