AFAIK, there isn’t any way to conditionally set the connection_scope parameter based on the social connection the user is authenticating against.
As a workaround, you could append all the scopes you need in the request. This should, in practice, only receive access based on the scopes granted and recognized by the authorization server.
So, in cases where the scopes only apply to Google, then only these Google scopes will be used. And vice versa when using Apple.