The example for the "Requesting authorization" section (note: section titles in the doc don't use title case) is currently:

https://critiquebrainz.org/oauth/authorize?
   response_type=code&
   scope=review,vote&
   redirect_uri=http%3A%2F%2Fwww.example.com.com%2Fcallback&
   client_id=yDDvwAzPUnoD8imvTpVm&
   access_type=offline

However, the parameter overview only documents response_type, client_id, redirect_uri, scope and state.

It also looks like the code indeed does not support it, and does not need to (the API docs suggest a refresh token is always generated). So please update the example.

In addition the MusicBrainz OAuth2 service also supports an "approval_prompt=force" option, to request a prompt even when the requested scopes have already been granted.
This seems like a useful option, so unless CritiqueBrainz has that as default behaviour, it would be great if this could be added.