> This is more akin to an electrician being called in to rewire the kitchen, seeing a locked basement door, picking the lock, and rifling through the boxes in the basement to find illicit materials.
Which still produces admissible evidence. Government agents are bound by the constitution when it comes to searches, private individuals are not. There can be other clauses in a state's constitution that enshrine an expectation of privacy that may be usable to dismiss such evidence, but as far as federal law and the US constitution is concerned a private individual can break a window into your house, find illicit materials, report them to the police and some time later you are sitting in court defending yourself.
> This was the FBI trying to skirt around the 4th amendment by having someone unrelated to the FBI do the seizure and search bit of investigating, so it could be done without a warrant.
Yup, and now that there's evidence such reports are being rewarded they screwed that up. If a government employee requests or incentivizes you to perform a search on their behalf you become an agent of the government for the purposes of that search, 4th amendment applies and if such activity is discovered the evidence is inadmissible. Incredibly stupid move of the FBI.