Completely inaccurate information
Users on tor can get unique and or shared UIDs by using tor gateway like whonix. (Yes you can sometimes share an ID with another user if you are on the same tor gateway.) Most less tech don't know this and leverage 000000 id. (they use out of the box tor browsers and tools etc.) If an anon uses whonix the user can get a unique ID. The shills use the 000000 id because most shills want to supress content. Most anons filter the 000000 shills so the anon will miss content from real anons using standard tor techniques.
BTW Everything is recorded and nothing is actually deleted so it doesn't really matter anyway. Using anon operating systems and tools doesn't necessary mean you are anon unless you are manage your own gateways. So most that think they are anon on tor are not because they don't understand how it actually works.