Call it "median developer" and I'm OK with that. Average is a different thing. Median developer is by definition a developer that is better or equal to 50% of developers.
> the turning of something abstract into a concrete thing or object
We're talking abstractions from the start. The only abstraction all my posts here rely on is the assumption that skill level is 1-dimensional. And you started using that assumption (by referring to average developer).
Real world example:
There are 10000 programmers. Many of the programmers that are just starting to learn have similar skills to each other. Some of them work for a few years already. Their skill levels start to diverge. Many of them never develop their skills too much (because they never need to and aren't self-motivated enough). Some of the programmers got lucky, work in places that allow/require them to learn forever, and become very, very good. There are few of them, and their skills vary widely.
There are tons of people near the bottom, and very few people near the top. It's natural consequence of the amount of work and focus it takes to move from the bottom to the top.
Ranking them hides some of the differences, but not all (because it's much more common for people to have the same rank near the low end of the spectrum, where there is much more of them, than near the top - where there is just a few people separated by big gaps). So, when you took ranks from these people you would get sth like below (1=worst, 10000=best, if your ranking works the other way - reverse it it still works the same)
[1 (repeated 20 times), 2 (repeated 15 times), 3 (repeated 10 times), 4(repeated 5 times), ..., 100, ..., 10000] - so the distribution would still be skewed and the average would still be different from the median value.