just tested this myself and it does work, you may also need to have these settings turned on in options > online
Make sure that you are in online mode, the wifi symbol in the bottom left of the game screen under the minimap should be all white, not grey. Then teleport around all these locations until you find one, should find one after a while
https://www.youtube.com/playlist?list=PLnvJ6_47HHygXy4KCgtU6tgJCci9rFkoj
It's an interesting idea and not one I had thought of exploiting in the past. It makes sense that this is how it would work, as disabling a fort sets your reload location to that fort without setting you on mission. So any quitwarp/cheatwarp/death would spawn you there. However I don't think it would be useful in any situation, the main reason being that the spot is a long way away from the fort, about 600m away and on the Jackdaw. If it took you to the actual fort and set you on foot then it could be very useful. However this does give me some ideas for things to test so I will try those and get back to you if I find anything.
Late reply, but this only happens on mission replays, not in fresh games
Speedrun.com reccomend keeping all entries, even if they are obsolete, I would keep.
Regardless of it being a recognised category or not, I would be interested in watching it run.