I think you're taking a slippery slope argument well past the point of reason.
For starters, there'd be no reason for constant investigation: once you've completed an investigation, there is no reason to have another investigation in response to a similar report. At worst, every family would get a cursory investigation once. Admittedly, that's not great. Realistically, that would not happen either, as CPS does not have unlimited resources and would of course prioritize their time. So, the more people make spurious complaints, the less likely they'll get investigated. Similarly, it's pretty trivial to identify cases where someone is just spamming the system with complaints, and deprioritize it accordingly.
While it's not unusual for complainants to exaggerate, it's also not unusual for complainants to understate; you get a call about a family you've never heard of before, from someone who has never called in before, you just have no idea what you're going to find.
> Or you can be a black man with a white stepdaughter, or a white-passing daughter, and literally get authorities called every time you walk outside with her.
...and again, in that case, you're going to learn to ignore those calls pretty quickly.
Imagine how that'd work. If you called in a complaint about a ten-year old today, the kid would no longer be a minor by the time the investigation began. ;-)
No, they don't. CPS does not need to investigate observations that, even if they are true, imply nothing. That's just sentencing everyone who deviates from orthodoxy to constant investigation. CPS should be investigating claims of something and should have clear standards for those claims instead of being aggressive as a defense.
Or you can be a black man with a white stepdaughter, or a white-passing daughter, and literally get authorities called every time you walk outside with her.