What's the incentive for Google to EVER give the accounts back? If they wrongly deactivate an account (like here), you get a bad article, EFF and friends ruminate about your behavior, and the world mostly moves on.
If Google wrongly gives an account back, you get a different article: "Google helped child pornographer even after discovering CP in their account". Now that gets attention. That's a scandal that leads to political action, criminal charges, etc.
To be clear, I'm not advocating for how Google behaves. They're a lot more like a utility and probably should be treated like one (alongside the protections and requirements that come of a utility, you don't hear "eletric company stopped serving house since man suspect of CP lives there").
For the responses saying "Well the police cleared them", again I don't disagree. But if you're an executive making this decision you're thinking:
1. We never give back an account in this case and avoid the massive downside risk
2. We go through a lot of work to design a process that will impact a marginal portion of customers and really really hope nobody manages to social engineer themselves past, and pray that no enterprising news outlet/politician tries to make the "Google helped CP person recover their CP story" - they already have a target on their back.