They're becoming the norm for newer systems written in Python though. So I don't think the language is enough information to go on. This heuristic simply biases against languages that have been around a long time because more of their code was written before practices evolved.
"Python codebases with type annotations and type checking enabled" is not the norm. Consider a random file from the famous `pytorch` framework.
https://github.com/pytorch/pytorch/blob/main/torch/_functorc...
Even this file does not have type annotations everywhere.