I read the book Topgrading a few years back, defined A-player relative to the position: "An ‘A’ player as defined by Topgraders is one who qualifies among the top 10% of talent for the compensation available for a position (any position)."

I think this concept has been understood for many years in industry. However, In startup land, its been ego-cized a bit through logic like "people are the most important assets of startups, therefor there are good people and bad people, only hire the good people". But this logic alone is open for misinterpretation because whether talking about "A-player" or "10xer", good is much for a function of ability of an organization to empower a person in a position.

On the other hand, there is a reality that certain individuals will be an "A-player" more consistently in more positions than other individuals.. so I believe there is some value to understanding how an individual's general behaviors would, or would not, make them an A-player in specific positions. At the same time, its likely very difficult to deduce this kind of statement meaningfully unless the same person has worked with someone in multiple positions.