This drives me mad too. However, not sure it’s the end of the world. In many cases these are extra shortcuts, analogous to key bindings. Power users are (should be?) aware of the existence of such things and look them up. It’s hard to make keyboard shortcuts discoverable (though IntelliJ does a good job).
I think it’s extremely problematic when these are core UI actions instead of shortcuts. Manipulating long form text is quite annoying without the space-bar trick for example. Hard to see how you’d make that discoverable though. (An interesting UX thought experiment!)
The space bar trick is clearly explained in the iOS manual. Probably even in the Tips app too. At some point there is just no way to get people to know every feature short of forcing them to read the manual and locking the phone with a quiz on it at the end.
I think it’s extremely problematic when these are core UI actions instead of shortcuts. Manipulating long form text is quite annoying without the space-bar trick for example. Hard to see how you’d make that discoverable though. (An interesting UX thought experiment!)