Row Level Security: Default Role Assignment

I attempted to use Row Level Security (RLS) for the first time, walked through the MS post i found. I set up the roles, and then applied the rules/filtering to those roles, and it was easy. I then published the report and went into the workspace in the pbi service, and performed the testing function for Security settings, and they worked like a charm... however, then i started getting pinged by users whom i had shared the direct link to the report with, that when they attempted to access the report they were blocked. My assumption was that existing security would not change, and that I would go into the security settings within the service and add users to the roles i had set up under RLS so that just those users would have the rules tied to the roles applied only to them, leaving everyone else that had been given the link unaffected... what actually happened was the exact opposite, that everyone was locked out, and i appear to have to now go in one by one and assign everyone a role?!?! Am I understanding that correctly, because that sounds really upsidedown... the majority of users to whom I have given permission should remain unchanged (without any restrictions applied from any roles i set up in the dataset using RLS), and I should be able to apply the restrictive filtering X role only to the small handful of people that need to be restricted. Is there a way to do this currently? If not, it sure would be nice if that could be set up.