I have argued for a while that the Fediverse is way behind in this area; part of this lack of tooling and reliance on user reports, but part is architectural. CSAM-scanning systems work one of two ways: hosted like PhotoDNA, or privately distributed hash databases. The former is a problem because all servers hitting PhotoDNA at once for the same images doesn't scale. The latter is a problem because widely distributed hash databases allow for crafting evasions or collisions.
This is from the study's author (here's the full thread). It shows how pernicious centralization is in technology. The author is claiming the fediverse is "behind" instead of the tools behind behind in supporting decentralized services. They were developed with only centralized Silicon Valley silos in mind and now they can't keep up with a decentralized infrastructure and the authors solution is for decentralized services to centralize around these tools.