TMP435 IBIS Model Question

According to the TMP435 datasheet, SDA signal need using  an external  pull-up resistor as it is an open drain buffer.

But when I use the ibis model (download from TI website) ,the GND_clamp V/I curve of  SDA_3 model have 2.5mA current in 0V.It just like an internal pull-up resistor exist.

So my question is whether an internal pull-up resistor use in the pin 9(signal SDA)?Is the IBIS model accurate?