I would consider the words of AndyP to speak truthfully about issues in the game.
I am not going to go an link through Phab and other sources to prove that issues on this topic exist.
I am not going to argue about whether or not there are issues in regards to sector boundaries and crossing them, there are many confirmed issues recognized by both Schine and a majority of the player base.
Now the next logical step in the discussion is whether a larger sector size versus a smaller sector will produce less issues.
Simple math can prove that one ship moving at a constant percent of sever speed will cross more sector boundaries with smaller sector sizes over a course of time than a ship moving at the same exact speed over larger sectors in the same course of time.
You want math I will give you some.
Take Ship1 moving at a constant rate of 100 m/s over a course of 3 minutes. Ship1 will cover a distance of 18km over the period of time.
Config A has a sector size of 2km, that means that Ship1 will have crossed roughly 9 sector boundaries if it started at a boundary.
Config B has a sector size of 3km, so we see that Ship1 will have crossed roughly 6 sector boundaries over the same time period with larger sectors.
To reiterate the point I was trying to make.
Sector boundaries cause issues. (Confirmed by players, sever owners, and Schine)
Sector size increases will reduce the number of boundaries crossed over a period of time.
The math to support this is simple and server max speed is a shared limiting factor for boundaries crossed over time vs the distance needed to cover before crossing another boundary
I would love to see the work of the 3rd party and the math they use to validate what ever claims they reach.
As to the topic of "how much" is a good change I can't say, not many can without people willing to test changes.
Edit: I am also done at this point, you made it clear you no longer wish to see the topic.