If anyone proved such a result, I'm sure they would be awarded a prize of some kind.
It's obvious that the time/space complexity of a program can stay fixed while you arbitrarily raise the programming complexity of a program by arbitrarily raising the number of branches that are rarely taken, an action that won't affect the asymptotic time complexity of a thing.
And sure, you can talk about the Kolmogorov complexity of a string of computer code, but the minimal string representation of that code is unlikely to be one that a programmer would describe as simple. Even minimizing the string that would behave as that of the original program is usually non-desirable.
https://en.wikipedia.org/wiki/Programming_complexity
https://en.wikipedia.org/wiki/Computational_complexity_theor...
Bubblesort has inferior time complexity than Timsort, but is simpler. The bounds of the comparative sort problem doesn't tell us that either.
A lot of real-world CRUD code, for instance, does nothing of computational interest whatsoever, but it isn't simple, because it has to cope with real-world business-logic complexity. (And possibly a lot of complexity beyond the necessary complexity, due to poor design, changing goals slowly messing up the code, etc.)
> You can describe the complexity of "code understanding" as the computational complexity required to answer a question about it, say the time it takes to find it or the length of the proof
I don't follow. How are proofs relevant? A programmer having to wade through poorly-named functions and a lack of documentation, is not well modelled by computational complexity theory.
> You could even talk about the simplest sorting algorithm as the one with the shortest proof.
Who'd care? That bears little relation to either the complexity theoretic properties of the algorithm/problem, or to complexity in the informal sense.