It seems like the league has a smart and easy out here. It can state that it accepts Onana's interpretation, drop any punishment for Garnacho, and state that it takes the issue of racial abuse seriously, as evidenced by this thorough investigation, so players must be mindful of their social media conduct.
Done. Dusted. They don't punish a guy who doesn't appear to have done anything untoward, and look like they are actually willing to back up their policies.