Current, the process and thread policy works well 600 vusers. with 600 vuser it will generate 20 processes automatically. However what if user choose to run 1000 vuser? It will generate 30 processes..
It's not recommendable to do it because more than 20 processes may causes the memory size problem..
If the processes are more than 20, it's better to increase thread numbers..
Reflect this to default policy script.