How is muscle memory an exclusive benefit of CLI? How is response time superior for a CLI? I've used GUI tools for git professionally for years and it seems much faster, safer, and easier to use. I've had peers that use CLI instead and they appear to struggle for all the expected reasons (poor feedback, poor discoverability, etc).
I have a few commands and one-liners that perform certain tasks. I can chain them together without looking at the screen. In fact, I can be reading code on the editor while I perform them on the terminal from muscle memory alone. I build a mental model of the branch I'm working on and how it relates to trunk and work from there. Each command updates that mental model. A GUI will never be as fast as that.
Now, you're right - a GUI that can be fully navigated with the keyboard can get somewhat close. That is, until an update changes the place of a button, or the organisation of a menu. CLIs almost universally have stable contracts with the user.
Don't get me wrong, I like GUIs for a lot of tasks: web browsing, CAD work, even programming. I just find that "everything should be a GUI" only serves to bring top performers down closer to the mean at best.
Furthermore, a crappy CLI is really only crappy until muscle memory sets in. A crappy GUI generally remains a crappy experience for as long as it's used.
Is muscle memory an exclusive benefit of CLI? No, but it's am universal benefit of the CLI, whereas it's only incidental on GUIs.
In my experience, a GUI can chain command together for you and invoke them instantly or automatically, no typing, no looking. It would really help to understand what tasks you're doing that you feel CLI excels. They're certainly git commands GUIs handle poorly, but they are usually arcane and infrequently invoked. I'd hope you'd agree there are cases where the GUI excels.
GUIs are (usually) slow and break the flow. They cater for the bottom of the pile of users, in detriment of the top.