Looks like an error in the Docs
OAuth Authorization Code Flow (User Access Tokens)
Shouldn’t be
Use this request:
GET https://api.twitch.tv/kraken/oauth2/authorize
?client_id=<your client ID>
&redirect_uri=<your registered redirect URI>
&response_type=code
&scope=<space-separated list of scopes>
It should be:
"Redirect the user to this URL via GET"
Edit: was about to flag this to the devs… but I already did…