The allegations here are that the two pedophiles used the seal of confession to hide their mutual crimes.
I am not a canon lawyer, but if you I go kill someone, and then confess it to each other and say all is forgiven, that is at best very irregular.
For the record, I am not for breaking the seal of confession. And if a lawyer argues otherwise, he had better report any illegal activity his clients do.
The situation you describe is covered under canon law under “solicitation”. It is considered extremely serious and the penalty of excommunication is mentioned not only for the confessor, but also for the penitent if they don’t report the solicitation to the bishop within a month if possible.