Wikipedia states that they use the "normal" (not inferential/gossip) mood, because otherwise it could be taken as a value judgement in some contexts.

https://en.wikipedia.org/wiki/Inferential_mood

You still use this tense if you are just reporting what you heard on news. What matters is that you have not witnessed it, just talking about what you heard on news. “There was an accident.” “Kaza olmuş” (the alleged gossip tense).

If you want to emphasize something matter of factly, you might use the normal past tense (kaza oldu) but that might imply you seen it yourself, you you might get asked if you were actually there.

In something like a history book, past events usually mentioned by a combination of this reported speech and past tense of the “do” verb: “Kaza olmuştur”

To sum up, it is not specifically a gossip tense. If you were not there, even if you are certain, you use reported version.

In the news they use "known past tense", like "gel-di". The article above mentiones "learned past tense", like "gel-miş".