Not true. The penitent is not bound by the Seal of Confession. The priest and anyone who overhears the confession are bound.
The penitent can do what they want, of course, but he is advised to not write it down, and advised that it is never a part of forgiveness to do so nor to dwell or obsess
In a piece on why can’t Catholics do confession via email, it can’t be done. The Church doesn’t want anyone writing down their sins, and for the reason depicted in this story