RICHT - thank you. When was this in your case?
I remember having this highlighted at a CO visit when I was an elder in the UK - I would say about 2003/4? It was used to remind us of the "very rare" possibility. BUT we were told not to "offer it" but contact the branch if someone "claimed their baptism was invalid". Also that if anyone had "progressed" to being a pioneer (even AUX) MS or Elder that it could not be "undone" for any reason as that showed that the holy spirit had obviously approved them for further service. (BARF!)
It COULD certainly be used if someone was baptised before the age of maturity (18 in UK) AND that they confess or it was proven they were sinning (DF level of sinning) all the way from before to after baptism.
But the 2017 WT article above may have changed that - perhaps it's in the 2015? (not sure of the year) Branch manual on the ARC website?
I could envisage the Borg using it to their advantage - you know Brother "Molester" has his sins come out and it transpires he was doing it at time of baptism so the Borg nullify it to claim he was "never really a jw" especially if he was inactive and a jw in name only - but that could be me being cynical!