I think I found a way how to use it.
I was trying to fix the problem with Big Doors tiles in vanilla tilesets. These tiles are L Pathnode shaped but with doors in middle. They are set as Pathnode N with DoorVisibilityNode Y in set file. This doesn't work. Player only needs to come closer to the doors and it will reveal everything behind them.
I tried many many setups but Y never worked as it should.
To my big suprise, when I used Pathnode N and DoorVisibilityNode T it worked as it should. I tested both sides, and the map behind doors get explored only after opening the doors. Also tried DoorVisibilityNode P but this one explored map behind doors only from one end.
I haven't tested anything more atm. Maybe it reveals something more, im not sure yet, I just thought I will share this as it could be used to interesting things.
EDIT: it has one little downside and thats when pc spawns at this tile, he won't see surroundings of the open end. Still worth it.