While scientific studies on the efficacy of postpartum girdles is limited, anecdotal "research" from real parents would suggest that these garments offer benefits after giving birth.
The support that girdles provide is designed to improve posture and stability. They give gentle compression that may help in recovery after birth.
Just make sure that a girdle isn't so tight that you can't breathe or comfortably move. Wearing a compression garment that's too tight can have negative health consequences.