If you make the token on someone elses site.
And their ClientID gets disabled, your token stops working
If they reset the Client Secret, your token stops working.
If they suddenly drop off the face of the earth, your token stops working.
Additionally, they may use a Legacy Client ID, which means tokens it makes last forever. Soon™ Twitch will expire all Legacy Client ID tokens.
Which means, your token stops working.
And because you don’t have the client secret, or the refresh token you cannot make a new token. Which means, your token stops working, and you will HAVE to make a local server to generate an access and refresh token one time.
Additionally, whenever you change your password using forgotten password on Twitch, all your tokens for all services stop working, so you’ll either have to reuse the site or jump thru your local website. Thats assuming that their site is still around and working.