First, that "teak" flooring looks really nice. Was that done by the previous owner?
What I believe
"Be Free" was referring to is from the factory design, the vent needs to be plugged else water can slosh out, especially while heeled. This refers to the original factory design.
From the Factory Manual
If the valve or vent plug is open, even slightly, the motion of the
boat can drain the ballast water from the tank or allow the boat
to fill with water. If either the vent plug or the filling valve is
open, ballast can be lost when the boat leans over under sail.
YOUR boat's vent has been modified so this does not apply. What it appears to me is that the previous owner extended the vent from the base under the cushions, with some tubing to that fitting that allows it to vent without the need to open the compartment to get underneath.
There are many ways to accomplish this. Many owners have simply done similar to yours and ran the vent tube up into the anchor locker.
The purpose of the ballast vent is to allow air to purge the ballast tanks while seawater is entering the main valve underwater on the transom.
The mod link I posted above ran the vent to the aft so the captain could see/hear the air rushing out.
Here's another much more complicated mod for the vent. It accomplishes similar results. Negating the need to go forward to open/close the ballast vent.
https://macgregorsailors.com/mods/index ... em&id=2094
What I believe your previous owner did was to raise the vent opening so water can't slosh out and route it to the inside of the cabin to make it easier to open and close.
In my opinion, that "fan-like" thing appears to be a sink drain fitting. My guess is the PO would open/plug it from inside the cabin negating the need to lift cushions to get to the factory plug. It's very clever and another way to raise the vent well above the water line so water can't slosh out when full.
With all that said......
you should NOT leave the main ballast transom valve open while sailing! If I understood your post, you only close it when emptying the ballast or at the dock to keep critters out.
From the User Manual (you can download from the main site "Resources")
EXCEPT WHEN FILLING OR EMPTYING THE
WATER TANK, NEVER OPERATE THE BOAT
WITHOUT SECURELY CLOSING THE
TRANSOM VALVE AND VENT PLUG. If the
valve or vent plug is open, even slightly, the motion of the
boat can drain the ballast water from the tank or allow the boat
to fill with water. If either the vent plug or the filling valve is
open, ballast can be lost when the boat leans over under sail.
You may think the tank is full, and that the boat is self
righting, but you may be unpleasantly surprised by an
unexpected capsize. If the transom valve is left open, the
forward motion of the- boat can drain the tank, resulting in
capsize
It's okay to leave the transom valve open while the boat bounces around to ensure all the air pockets have been purged. But once full, it should be closed. ESPECIALLY if the vent is not airtight!
If the transom valve is closed, the vent does not need to be sealed shut because water can't escape.
I hope I've explained this correctly.