Is it legal? Sure. Is it allowed as per Envato’s terms and policies? Certainly not. Is it a lame way to appear more competitive while giving the finger to your whole community? You bet it is!
You cannot make that assertion. Depending on the case, buyers may be responsible for paying performance royalties. Some broadcasters are indeed buyers here. Restaurant or bar owners are responsible for paying performance royalties. Some of them exclusively buy performance royalty-free music because they want to avoid paying PROs. Same thing with event planners,… These cases are in the minority of course, but they do exist.
As for AdRev, this is fear mongering plain and simple. No there is no legal issue when using AdRev registered music. Envato has asked several authors to remove such texts (those texts were very similar to this one… same author?). Since non registered music, especially those that are advertised as such, are easy target for claim usurpers, they absolutely cannot guarantee there won’t be any issue, as legal problems do arise from such situation where author is not the claimant.
You should definitely report the author to support. But I don’t think this has any impact on the type of broadcast license buyers choose.