it doesnt matter about seed mode, all we know is that when seed mode is in that person, he becomes more stronger. and what we call it "IN THE ZONE", its jus a time where everything connects with no limitation.=D that is also wut coordinateS are lines connecting....maybe thats why they are called COORDINATORS... there is no logical explaination for seed mode, never explain in GS or GSD, shinn is on battle mode most of the time u dont c him on seed mode so easily. kira can activate so easily because he is... again..... the ultimate coordinator,(ultimate coordinator(coordinates)..??? easiest to connect in the zone maybe....=P he gets In The Zone the easiest.

quote-When a character suddenly resolves to protect their allies or to strike down their enemies, SEED mode is shown as a falling seed which bounces once and explodes.

1.that is the only time nessary to activate it....oviously, no one is gonna need that much concentration walking around......

but know this kira can activate right from the start while shinn or athrun take him a while.