From the description of the behaviour of Dynamic Simulation (https://community.bistudio.com/wiki/Arma_3_Dynamic_Simulation) it seems that the behaviour of the Dynamic Simulation Manager behaves differently on server and client side, which does not seem to be the way its described.
When a group under dynamic simulation has no trigger unit nearby in the range of dynamicSimulationDistance "group", then it will not be longer simulated and simulationEnabled = false on dedicated server side for this unit as expected.
On client side the same unit will stay simulated (simulationEnabled = true all the time), however it will not move as it gets no position updates from server anymore, they often keep walking at the same place until they get simulated on server side again.
Problem is that these units still eat up alot of performance on client side. The behaviour does not change if the group is under dynamic simulation on client side or not.