My Lattitude E9430 Has a half Mini slot available?

Took it down to do a good cleaning and whoa! there is another half-mini slot (labeled “sata flash”) right next to the WLAN and WWAN slots.

Question: Is this useful for an SSD?

I’d like to use either a Pcie or SATA drive, I wanna boot W10 from it, so a size of 24g would work great!

Have searched around and have found no for-sure info. Probably for flashing bios or some other proprietary data during build.

Again, there is a third slot labeled SATA FLASH. I have only found threads that address the WWAN and WLAN ports.