Hi there-
Repair of the muscle damage caused by pregnancy or weight gain and loss is important in the achievement of the best outcome possible, and should not materially increase your risks related to the procedure.
Significantly, it is important for you to also understand that if you were to look for a surgeon willing to do a tummy tuck on you without tightening your muscles, you will find one, only to realize (assuming that you are having a tummy tuck because you need a tummy tuck to look your best) after surgery that your don't look anywhere near as good as you hoped, or as good as other women who had a more complete tummy tuck.
In other words, repairing the muscles should not increase your risks, and omitting this important detail will put you at risk of being unhappy with your outcome.