It will still have leakage. But which means the baby knows there is something wrong then they will understand they should go to toilet instead of VV on the pants. This is a way to teach them VV on the pant is wrong.
Don't think that they can replace diaper to absorb all of the VV.
Only that they are a bit better than the thin underwear. This is a transitional period and better to do it in summer time.
During sleep and going out better to use back diaper.