Regarding ulterior motives - these permissions are 'performative' in that anything you can give it permission to do, it already has the ability to do. They're app level - not OS level. So if they wanted to do something, it wouldn't require you to give permission.
The app is split into multiple layers.
Just like your browser can do everything already, but only lets websites use specific features.
To be clear, I'm not accusing Anthropic of being evil black hats trying to break my computer, I'm accusing (or rather suspecting) them of pushing me towards some kind of product lock-in by making my preferred "sceptical at-arms-length user" workflow more annoying.