IMO yes the torque on any sealing surface is important. In this case like Dan0617 said - too much tightening on the 4 bolts could tend to cause the sides to deflect.
HOWEVER I took a close look at your pictures . The gasket seems to be encased between metal on 3 sides and it appears that the gasket is a little below the 2 surfaces on the sides.
On your head I noticed bolt patterns for a standard valve cover around the seal area of the head. I would look there closely to make sure your not just torqing metal to metal with minimal gasket contact. If you had some dykem blue you could coat those areas and then put the cover on by hand and move it around a little. If the dykem is removed then there is conack there and you should see the evidence on the valve cover