Simulate a model using smoothed shocks (using simult_)

Dear Dynare experts,

I usually use simult_ command to simulate my model using smoothed shocks as follows. The following is what I did to simulate Smet&Wouters 2007, Dynare code from this link:
sites.google.com/a/nyu.edu/jerome-williams/smets-and-wouters-aer-2007

y0=oo_.dr.ys;
dr=oo_.dr;
iorder=1;
ex_=[oo_.SmoothedShocks.eta_a oo_.SmoothedShocks.eta_b oo_.SmoothedShocks.eta_g oo_.SmoothedShocks.eta_i oo_.SmoothedShocks.eta_r oo_.SmoothedShocks.eta_p oo_.SmoothedShocks.eta_w];
y_=simult_(y0,dr,ex_,iorder)

I expected this simult_ command would give the same result as Smoothed Variables which Dynare automatically saves in oo_.SmoothedVariables… But there were slight difference between them.

Does anyone know what makes the difference?

Best,
Leo

See [Counterfactual simulations based on smoothed shocks)