Hi,
If you are using this page, note that the main purpose is to demonstrate the convention of PyTorch and its similarities and differences with numpy, etc. So, they are not really focusing on teaching deep learning stuff.
On the other hand, bias is not mandatory in learning models and can be omitted. For instance, in another example on this page (this link), it uses torch.nn.Linear(D_in, H) and in the comment it says that it calculates weights and biases. Although, if we see the documentation of nn.Linear, we see that bias is optional argument.
bests