This cvar has an impact only if geometry are not added for children. It removes implicits from the Dynamic Collections, and recreate then from the rest collection. Using this cvar could have an impact if geometry are updated from the dynamic collection on the GT, then those changes won't be ported to the PT.
Usage
p.gc.RemoveImplicitsInDynamicCollections [value]
Set via the console (~) or in DefaultEngine.ini / DefaultGame.ini.