Won't work, the limit is BIOS/CPU related from the looks of it, basically anything over 13 regular cards will not post properly on this board.
If that's the case then there is no point buying this mb, I'm better off my Asrock mb
The Asus B250 will work with 19 cards, but above 13 you need special mining cards to get them up to that point.
So it still has its place - I have 7 of them, only running 12 cards though, but the last 3 rigs I have run on Asus Z270-A boards, they are all equally stable.