Doesn't the Peter Principle come into play here? What if we do the same job but I do it twice as fast? That doesn't mean I'd be a good fit for the next level up, it might just mean I'm really good at doing this specific job very quickly.
In my mind this is one of the cases where "Jr" and "Sr" titles can be useful.
Or a 20 hour work-week with full salary.
I suppose it's ambiguous but generally I feel like "senior" means "responsible for more pieces or higher level pieces" not just "faster at the simple stuff".
Where I work, there are 4 levels of my job, none of which are management. That is to say that someone can work an entire career as a research associate and take on more responsibility, but not be forced up the org chart. This is very important because I look to the people in the higher levels for a lot of help (both organizational and technical), but we can do much of the same lab work.