Go is absolutely one of the best programming languages for LLMs for the reason you say, and Python is just what LLMs like to use to write short throwaway scripts. Frontier LLMs are generally pretty good at most programming languages and can pick up new ones pretty quickly. Training data seems to mostly just increase the speed which they write code, for example, GPTs tend to write Rust and Python faster than other programming languages.
For actual output quality, the main deciding factor is simply how much tooling it is there for the LLMs to check their own work, as LLMs seemed to avoid using a lot of libraries in general. That's why C# is underrated due to the tooling strength of the .NET ecosystem, as long as you tell LLMs to avoid using reflections unless absolutely necessary.
C++ is also surprisingly good, but you pretty much have to tell the LLMs to treat it like Go and don't use any of the dangerous features for normal code.
For actual output quality, the main deciding factor is simply how much tooling it is there for the LLMs to check their own work, as LLMs seemed to avoid using a lot of libraries in general. That's why C# is underrated due to the tooling strength of the .NET ecosystem, as long as you tell LLMs to avoid using reflections unless absolutely necessary.
C++ is also surprisingly good, but you pretty much have to tell the LLMs to treat it like Go and don't use any of the dangerous features for normal code.