Grinding loose Green Tea for more concentration
Grinding should not increase the flavour concentration, unless you mean increase the amount of tea you can fill a container.  The quantity of leaf and steep time would play a bigger factor in the strength of flavour.  However, if you powder the tea the main benefit would be shortening the steep time.  Which can also be a drawback as you have a higher chance to over steep and bring out unwanted bitter and/or astringent properties out into your tea.  For more information on powdered green teas and usage, look up "Sencha" and "Matcha".

Note: If you are wanting a stronger tea flavour you should consider the stronger end of the tea spectrum.  Such as Oolong (e.g. Tieguanyin aka Iron Buddha) (e.g. Pu-erh, Goishicha) or Post Fermented Teas.