I guess I was mistaken, I saw it in a post here Auth Code with PKCE - Refresh Token.
I also saw in the comments of this page Implement the OAuth 2.0 Authorization Code with PKCE Flow | Okta Developer that Okta doesn’t allow for refresh_token in authorization code with PKCE. It looks like the preferred way is to leverage the Okta session, however I think that means that it’s not possible to refresh without a redirect?