> to strengthen the bond in the cases where its true

You mean when the parental relationship is compatible with the wishes of the potential step father. Knowing that the child isn't yours can be useful in either direction. Either you know it from the start and accept it from the start, or you refuse it from the start. This idea that we shouldn't bear bad news and hide them, hoping to profit off the confusion, is a horrible way to run a society. Learn to deal with the bad news. (ignoring them is how situations escalate and get way worse than they should be)