Why not? Honest question--I haven't used fastai myself but my understanding is it's just a high-level wrapper API for PyTorch. Any particular reason why you wouldn't want to use it outside of the course?
We use it for training some of the models we use in production environments serving millions of requests per day, so there's no reason to exclude it completely IMO. As you say, it's a wrapper for Pytorch with a few extras tacked on.
With Pytorch you would either use pure torch, FastAI or something like Lightning most of the time. Unless you're using completely mainstream models such as the ones you could get from the Transformers library.
