An unfortunate fact is, similar to human with infinite time, LLMs usually have better performance on your specific langauge when they are not limited to learn or over-sample one single language. Not unlike the common saying "learning to code in Haskell makes you a better C++ programmer".

Of course, this is far from trivial, you don't just add more data and expect it to automatically be better for everything. So is time management for us mere mortals.