How did you come to the conclusion that he used Python? Just because it's easier?
If you were a Puzzle BTC creator in 2015, you could have used Bitcoin Core, Electrum, or Armory. Electrum (written in Python) was already popular in 2015, and its wallet format is well-documented. Importing keys via the command line (electrum importprivkey) would be trivial with Python-generated WIFs.
Python’s random.seed() function ensures deterministic key generation, unlike C++’s std::rand(), which varies across implementations unless carefully controlled.
Python’s random uses a Mersenne Twister, while C++’s std::rand() depends on the compiler.
Since Electrum itself is written in Python, a Python script would integrate seamlessly.
The same code works unchanged from 2015 to 2025 (thanks to Python’s stability).You just need to know the seed.