One possiblity is that the agreement was for non-decductible alimony and having the payment funded by a QDRO would shift the incidence of taxation to the ex-spouse.

FORBES: Penalty On Qualified Plan Withdrawal To Pay Alimony

For purposes of the recapture rule, the three year period starts with the first calendar year you make a payment qualifying as alimony under a decree of divorce or separate maintenance or a written separation agreement (do not start the clock if the payments were made under temporary support orders).

FORBES: Taxes From A To Z (2013): R Is For Recapture