Why: Krishna says he will now clearly explain his own conclusion on this relinquishment, since relinquishment has been declared to be of three kinds, promising to actually settle the disagreement just named rather than leaving it permanently open.

In life: after honestly acknowledging a genuine disagreement, it's still useful to eventually offer your own considered conclusion, rather than leaving the question suspended indefinitely once you've actually thought it through.

Teaching: after acknowledging a genuine disagreement on something important, work toward eventually offering your own considered conclusion, the way Krishna does here, rather than leaving the question permanently unresolved once you've actually done the thinking.