Internal SWDIO and SWDCLK pull up/down?

[dav01]

I know the question has been up before, but why does the data sheet say pull up/down ?

isn't the signals always pulled up?
or is there a scenario where the nrf52 would switch to a 13k pull-down!?

ARM ref:

[haakonsh]

It's should just state pull-ups. All pull resistors in the nRF52 series are 13k +/- 3k.