Is there something missing in the two sections near the end about the sinc function and limited time intervals? https://dsego.github.io/demystifying-fourier/#s

Is there something missing in the two sections near the end about the sinc function and limited time intervals? https://dsego.github.io/demystifying-fourier/#sinc-function-and-spectral-resolution https://dsego.github.io/demystifying-fourier/#sinc-function-...