It does not come out and say that in the book, but it can be extrapolated from Page 110.
It is extrapolated from the statement the
BRB makes: "Above a total of 1,999 points, the Force Organisation chart becomes a very limiting factor." P.110
So basically if the Force org chart is a limiting factor at 2k, it will also be limiting factor above 4k, etc.
If you are playing a 6k point game, you are hard pressed to find things to fit in two force org charts, though it can be done.
Technically more of a house rule than anything, but no one runs tournaments at 4k so it does not matter.