Obviously he isn't on the list because he didn't ride here last season and he has a average below 6.5. That must be the criteria which like the heat leader list hasn't been published. i don't think promoters help themselves by keeping these things secret. It could be said there is a reason to publish the heat leader list when all riders have been signed but there is no reason why the criteria cannot be published.
He rode here last season, Hans is a lower average and he is on the list.