What irks you about it?
Maybe the other problem is : Units are not in multiplies of 5 and that forces you unnecessarily to think. If it would be in fixed units like bootstrap or in multiplies of 5 ( pure-u-3-25 etc.) i would be less thinking while deciding the length of some div.
Why not use something like "2-cols/2-columns/pure-2"?
pure-row, pure-col-1-2.....