The OAuth 2.0 Authorization Framework defines the
authorization_code grant type and refresh token. It doesn't establish any rules for issuing refresh tokens and explicitly states in Section 1.5 that "Issuing a refresh token is optional at the discretion of the authorization server". One of the explicit goals for Rfc6749 was to enable offline access to protected resources when the end-user is not present. It does not define any request semantics for how a client can explicitly request a refresh token or whether that refresh token's lifecycle should be bound to the user's session that granted the refresh token. Authorization Servers are free to define these behaviors on a per-implementation or policy basis.
OpenID Connect being the identity layer ontop of OAuth 2.0 needed to define some new authorization server behaviors to enable end-user consent for when a client can access their identity info