[bitwize]

CSAM indicates you think the material, and the practice of making it, is abhorrent. "Child porn" is something some (severely deranged) people might actually want to see. The upshot of this is, if you put "ios child porn detection features" into Google, Google will see "child porn" and may think that's what you're searching for, put up warning banners reminding you that child porn is super illegal and that you should not be searching for it, and probably notify the FBI who will add you to a watchlist. If you put "ios csam detection feature" into Google, it helps Google know that you are not searching for child porn itself.

[colejohnson66]

What stops google from monitoring for “CSAM” as well? Security through obscurity (“if Google doesn’t know about the term, they won’t report us!”)

[bitwize]

Social dynamics. The kind of person who calls CSAM CSAM is unlikely to favor it, let alone distribute it, so people interested in it are unlikely to search for it by that name.