They could add M.2 slot on the back but there is nothing. Still if you don't need M.2 and use only 1 gfx card then it's as good as full ATX boards. Most other features are the same. Even X370 is quite poor chipset.
edit:
my mistake, there is M.2 slot on the back of the board, don't know how I missed it
edit2:
just got the Biostar X370GTN
