Did you even read the article, or just looked at the LaTeX formulas?
I'll give you a hint: Cmd+F "window". See any results? Because the DFT doesn't have a window function. The STFT does have a window function.
Second hint: look at the image in the article (https://substackcdn.com/image/fetch/w_1456,c_limit,f_webp,q_...). Do you think this shows the time domain and frequency domain representations (i.e. the DFT) of a signal? No, it does not. It shows the time domain representation, and the STFT of the signal, aka the spectrogram.
https://home.engineering.iastate.edu/~julied/classes/ee524/L...