They added "in app purchases" indicators in the store for this. I use it all the time. "In app purchases" on something that claims it's free is not free.
Most of these apps use dark UX patterns to trick new users into scammy free trials which convert to $100+/yr subscriptions after 1-3 days. These apps also make it difficult to close out of the subscription window, or make it seem like you have to subscribe when you don't.
It's entirely contradictory to everything Apple once stood for in justifying their gatekeeper App Store experience.
Apple could easily ban these types of scammy UX patterns, but they won't because it benefits them. That's my point.
I’m fairly certain this is because it’s the only way of offering a trial that Apple allows?