Curiously the last photo on the site clearly shows an SMA footprint, but the photos only show unpopulated solder pads. I wonder if you can order the board with the SMA socket populated?
It looks like it's set up so you could jump the antenna connection to the connector if you solder it yourself. The Zero W had the same setup (in a slightly different spot on the board), but has never been available with a connector pre-soldered AFAIK.