Give me a break with your "elegance". No matter how you twist it, it's subjective unless you provide some actual metrics. Once you do that, you might notice it's not "elegance" any more, it's something else.
Computers especially but science generally lead people to favor the quantifiable to a pathological degree. Software development, like most other complex endeavors, is stubbornly resistant to predictive quantification.
It's also easy to criticize other people's work, but it's a lazy path to being right. There are an infinite number of ways in which something can be considered inadequate or a failure. The number of ways in which a something is good or useful is much smaller. Find the terms on which it's trying to succeed and criticize it there, if you have to criticize something. But introducing your own yardstick and saying "you failed!" is cheap.
You're right that it is not something easily measurable.
The product of code golf is measurable. But, code golf is not usually what you want in production code. Performance is not about characters/lines of code and neither is clarity or maintainability, necessarily.
I don't think there is anything wrong with this sort of requirement. He stated there are no winners. Elegance could really be decided by the community.
Just try to write concise but clear code that would be easily understood by most who are well-experienced in the language/framework.
Try submitting the same code to the IOCCC [1], the ICFP programming contest [2], the computer language benchmarks game [3], and the Flux Challenge (well, assuming they had the same problem statement, and that you could emscripten your C code for the Flux Challenge). They all have prizes for elegance. The only one of their definitions of elegance that is objective is the benchmarks game, which defines it as straight lines of code (and has resulted in some entries that most programmers consider to be abominations "winning"). It's different cultures, different judges, and different criteria for what's elegant.
As of today, it is incredibly hard to evaluate frameworks because you generally only have the time to evaluate small examples, but those are usually easy to do anyways.
This thing here is as tricky as it gets for the scope. Even if the judging is subjective, it is highly revealing.