Unless the motherboard decided to go off standard, that's part of the size standard specifications. Full atx, matx, mini itx etc follow form factors which describe the typical size of the board, screw mounting pattern and so on. You might find a board like gigabyte's z97x gaming 5 that's listed as a full atx but is a little narrower and so doesn't reach the furthest screw holes near the right side of the board. The rest of the standoff's line up properly though.