Because the app is available to download for free, Apple will not take a percentage of the "in-game-currency"
revenue, correct or did I misread?
No, that's not correct. Apple take commission on all in-app purchase transactions.
The only case where Apple don't take commission is when you are selling things that are non used within the app - for example, physical goods that are sent to the user, as in a supermarket or food delivery app. But in those cases, you need to provide your own payment processing; you can't use In-App Purchase.
You may want to argue that "tipping other users" falls outside the "used in the app" definition. I don't know about that. It may depend on what the other users are doing that deserved tipping. For example, I guess you can tip your Uber driver and not pay Apple. But it is that aspect that matters, not whether the app is initially free or paid.
Note that in many cases the commission will be 15%, not 30%.
“On the iOS, iPadOS, watchOS, and macOS App Store, Apple charges a 30% fee for apps and in-app purchases.
However, the fee doesn't apply to free apps.”
Where does that quote come from?
Do read your developer agreement! It has all the answers.