If the engineers that originally implemented the function intentionally chose the slower version, a quick comment as to why would have prevented this from happening in the first place.
One of the first things you're taught when learning pytorch is that you're not coding in python, but actually creating a network graph that is loaded and executed on a GPU. Other common sense things is knowing that you shouldn't use stuff that is in the stdlib or in numpy and use torch.* variants instead, not doing so will incur either undefined behavior, cause massive memory copies between the CPU and GPU or most likely, error out at runtime.
Note that this is a repo that is forked from the official repo, it's a community repo focused on inference and thus doesn't care about training so it has completely different considerations than the original code.
This is idd the time to place a comment, yet so many people don't do that.