I made rolling alt flings, and you can too!

I feel like I'm the only one who really did any research

I'm not convinced 'an hero' is grammatically incorrect though 'a hero' is how it should be.

Doesn't it depend on your accent? If your accent makes you pronounce it "ero" (which isn't wrong, it's just alternate; if some authority says it's wrong, then it needs to be updated, because language is defined by the people that speak it), then you should say "an hero", because anything else would sound stupid. If you put a really good "h" sound on it, then you should probably say "a hero" because, again, anything else sounds stupid.

How is that difficult?

dat voice of pragmatism trivializing the inquiries into the minutiae of semantics, resulting in insight into the fundamental nature of language.
Classic Hedge.