is set_param(bdroot, 'SimulationCommand', 'update') required in R2013a?

Hello,

I am controlling a model with a workspace parameter. In R2010a as soon as I change this parameter, the new value is accepted and the model's output changes. In R2013a the new value is not accepted until I issue a set_param(bdroot, 'SimulationCommand', 'update') command. Was this a deliberate change made by Mathworks between these two versions? Is an explicit call to update workspace variables now required?

Thanks, Ilya