To me a Low SD indicates that you should minimise vertical dispersion at range because most of your shots are around the same MV.
Logically you would think that this tends to support tight groupings but anecdotal evidence varies.
Once beyond close range grouping all sort of issues can start dispersion which queers long range grouping.
Quirky winds, bullet no longer supersonic, mirage, not getting atmospherics rignt, ... a long list!
Either way a low SD (<10) is obviously desirable.