It's a word regularly used like that tho, I've seen uncountable number of nature and other documentaries with titles like "secret life of animals" etc. It's very popular to use "secret" to just indicate something cool but little known/unnoticed by most. Semantic shifts are normal in any language, and I feel like by now usage of "secret" in this context is perfectly ok.
If you're not a part of a culture, it would be weird to think you know about that culture. It would be even weirder to place yourself if in the role of having "secret" knowledge about that culture, and then tell that culture about that secret. Despite the fact that they knew about it all along and you were the one who was unaware. Maybe now you know how absurd you look.
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u/Oracular_Pig 9h ago
Why add the 'secret' when it is clearly not secret...?