Ok, if Direct sail is not part of 13 final then we can safely assume it has no responsibility or bearing on this topic. So the question remains - why does this happen? Why would "sail to" take ships that all heading on the same bearing and have them arrive on different bearings and well inside the minimum location teleport distance apart? When they spawn at the destination they are usually already in collision with each other if there are 4 of us but if they are ordered to heave to drift, they do not "sail to".
Here's what I think is happening- I think that "sail to" is the same bit of kit that gives us the ability to "fast travel" between destinations on land. which means that there is a scalar somewhere that defines where the ships are generated and how close they are to the intended spawn on sea the same as on land. The problem becomes amplified when there larger ships involved, such as battleships and MOWs. I suspect this is because the Ships have overly large " collision zones around them. Try coming along side a mow with any ship and you realize that collision begins at about 50 yards. Do the same with sloops and the distance is much smaller. So if you have 4 large ships ( bigger than corvette) the space in which they have to " arrive " is just too small to support them and doesn't have anyway to adjust. So it just trys to fit them in anyway it can. Imagine a box drawn around the "destination" that has a specific size. If there isnt any way to expand the box then everything just gets crammed into the box. Not a problem if the ships are small, but a huge problem with big ships. Like having 3 parking spaces and 4 cars, it can be done but there's gonna be some scraped paint and broken mirrors.
What I can't figure out though is why "sail to" would bring all the party's ships to the location if they have already been tasked, and why the heave to task prevents them. Ships that have been ordered to "sail away" will not be included in the "sail to" if they are beyond visual range(BVR) USUALLY, although I have had it happen that they occasionally rejoin the group for a hug. Not really a big deal unless I ordered them to sail away because they were on the verge of sinking, in which case a collision is usually enough to sink them.
There must be an instruction with in the "sail to" function code that tells it to move the entire group, just like on land. Perhaps when I tell the ship to "heave to" its like ordering a companion on land to " stay here" which I've never done but I assume it would stop that NPC to stay put while the rest of the group "fast travels".
Another interesting observation using "sail to" is that should I use "sail to" on a surrendered ship, the distance that I respawn at is larger than if the destination is active, provided I have no other ships in the group. I confirmed this when I had a lot of surrendered quarry( big battle). I used "sail to" whith all companion ships ordered to "heave to". On each successive "sail to" I ordered 1 ship to "defend' me. By my 3rd "sail to" ( now a 3 ship group) I practically spawned right next to the quarry and it was a scramble to get out of each others way. I think the next experiment will consist of me buying 4 puny gunboats and "sail to" a friendly ship. I expect that there will be no collisions even at full sail.