The external Pull-downs on Pin 18 (UART_RX) and Pin 26 (TMC) are to ensure that the correct state is asserted during power up. These are optional, but we use them internally as failsafe mechanism (i.e. we always add the
the 2 pull downs in all of our 2073XS based designs)
Pin 38 is not connected to the die internally, so we updated the datasheet recently to state NC vs. GND.
There is another thread here that talks about this pin: Re: BCM20732S pin migration to BCM20736S
Just a Note: A pull-down resistor on P18 is entirely redundant for any of the Modules('S') versions as there is already a pull-down internally.