I don't personally agree with the idea that senior is basically the end point of writing high level code. Perhaps it's just a difference in terms but I think of seniors at the high end of their capacity as being able to release high quality features. But if I needed a whole new app greenfielded, would I trust a senior to not only get the job done, but execute at a high level, with a clear vision, clean design system, beautiful code base, all the right choices of libraries, following all the best practices, linting, style, etc? Of course not.

To me, a staff engineer can deliver that application at that level, and can lead senior engineers in maintaining and enhancing it.

We also consider a level above that, the principal engineer, who is primarily focused on higher level and longer term thinking and less about individually jumping into tickets and features. They re-envision the entire approach to implementing the business logic and scale the business in ways that seniors are mostly helpless at. They do work through others much more, and I do personally see Staff Engineer as the highest level where you primarily are still coding day to day.