I have an example of a bad fruit of believing in BOD. I have heard of priests denying the sacrament of Baptism to Muslims and Jews because their conversion will cause difficulties. Instead of Baptizing them they assure the Muslims and Jews that they will be saved by Baptism of Desire so they really don't need to be Baptized. I think this is presumption.
That is insane. Who were these Priest? Having an erroneous belief in BOD that causes bad fruits. Simply believing what the Church teaches on it (nothing more and nothing less) does not cause bad fruits.
You think it is insane? Then I will tell you one priest who did this. Archbishop Lefebvre. I bet many posters on this site will not believe me but I heard this by listening to Charles Coulombe videos on youtube. Coulombe claims that in one of Lefebvre's books he admits this. I forget which video it was in because I saw many but I imbedded it on Cathinfo a while back so you might be able to find it if you do a search. This is what was claimed in the Coulombe video: He claimed that Archbishop Lefebvre, when he was a missionary in Africa was approached by a group of Muslims who wanted to convert and be Baptized. He was worried because he thought if he Baptized the Muslims and the other Muslims found out they would retaliate with violence. So he told the Muslims they didn't need to be baptized because they would be saved by Baptism of Desire. I believed the story and it is, TKGS, based on reality (Unless Coulombe lied about it).
If what you say about ABL is true he was bonkers. All are obliged to be sacramentally baptized when they are aware of the necessity though they do have to be properly schooled as adults first. If they tragically die before this happens then BOD would apply so long as they were sincere having a supernatural Faith and perfect Charity.
I don't believe he did it. But if he did I am not sure how he could have escaped a harsh judgement from God.
If he meant they needed to be taught more before being baptized and if they died before they could be baptized having the manifest intention to become Catholic they could be saved by BOD so long as the other requisites were present.