No,
It is permissible (though by no means necessary) for a priest to talk indirectly about some information he has or has not heard in confessions over the years as part of a homily or teaching lecture as long as he gives no information connecting this information to any specific person. For example, he could choose to mention "I've heard the confession of a murderer," or "I've almost never heard anyone explicitly confess a failure to help to poor."
What he must not do is reveal particular confessions, such that someone could identify the penitent or the penitent could know the priest was talking about him, but he can talk in generalities or discuss the number of times something is confessed.
Otherwise how could he discuss with other priests or his bishop the best way to deal with penitents who confessed sins A or B? He has to, at the very least, set out that such sins have been confessed to him.