The ADS5294 is an 8 analog channel device therefore there are only 8 SMA's for the analog inputs. It is the digital output that can be used in 1-wire or 2-wire mode. In 1-wire mode there are 8 LVDS differential pairs corresponding to the 8 analog inputs. In 2-wire mode, there are 16 LVDS differential pairs with each analog input getting 2 outputs.
https://e2e.ti.com/support/applications/medical/f/30/t/426573