You have the seasonal type set to 'Auto' in the model tab - I'm not sure what criteria gets applied in auto mode, but it is clearly not using seasonality in this case if you get the same estimate for each month. If you change the mode to additive or multiplicative, you get different results for each month, though they are still different from the factory. You'd have to dig into the results anchors to see exactly what parameters it is using for each model. Based on a quick glance the factory is using ETS(m,n,a) and the ETS tool is using ETS(A,Ad,A). I don't know enough about the underlying model to tell you how/if those parameters are different.