This is the most clean, grokkable, readable C++ code I think I've ever read. I feel like most open source C++ projects I read in non-game spaces are just a complete mess of indecipherable syntax. Is this game code uniquely well written or am I often looking at the wrong codebases?
This is because a lot of C++'s idioms are a) very old (stemming back from C++98, and slowly morphing with each version) and b) extremely conservative. Ideas that are important to more "modern" languages like KISS and "nothing magic" apply much less, as efficiency is generally more focused on. Especially in systems and embedded development.
> Is this game code uniquely well written or am I often looking at the wrong codebases?
I would say it's multi-faceted. Firstly, the codebases you're referring to probably aren't nearly as messy or archaic to primarily C++ developers. They just seem that way to outsiders; though there are plenty of messy codebases. Secondly, gamedev has it's own paradigms and idioms that are generally structured more agnostically and modular.
That all being said, I would say modern codebases built in C++11 and newer are much "cleaner" for non-C++ developers with more modern idioms.