reTerminal DM NVME physical size

The reTerminal DM has an internal M.2 / PCIe connector for expansion purposes (J7).

Can any standard NVME drive be installed into this slot? The manual says you have to use the dual ethernet expansion card … really?

If you can fit a drive directly, I assume it only supports 2230, 2242 and (maybe) 2260 due to space limitations?