Body Flange / Standard Flange

I need to do a simple Pipe Calculation 

Design Code ASME VIII Div. 1

design Pressure 16 bar / Temperature 120 degree (Celsius) / Material  SA 182 GRF316L


The first one is a Standard Flange (Welding Neck)

the second one is a Body Flange with the exactly same Dimension than a Welding Neck Flange.

Now the Calculation says that the second one (Body Flange) --> error 366 FLANGE N2: insufficient flange thickness (in operation).

So why is the first one OK but the second one NOT ????