...Watchtower has already made it clear that they will report a case of child abuse...
Have they?
Aside from where there are legal mandatory reporting laws in place the only reference I can recall to the WTS proactively reporting, regardless of internal judicial status, is in the statement to the ARC...
In circumstances where the elders and/or Branch office determine that a child is in danger, the elders will report the matter to law enforcement authorities even if there is insufficient Scriptural evidence to establish serious sin.
As yet, I don't believe this is the official, documented policy of the WTS even in Australia, let alone world wide.
Also, the above comment refers to a child being in danger. We are talking about here about child pornography so there is unlikely to be a victim known directly to the alleged perpetrator or to the elders. The direction given as per the quotes in the OP and the above quote show little evidence of there being a proactive stance taken to reporting someone who has committed the criminal offence of viewing child pornography.