Also as personal policy, when someone asserts something, is asked for evidence, and then comes back with "it's really well known and I'm not going to provide ev

Also as personal policy, when someone asserts something, is asked for evidence, and then comes back with "it's really well known and I'm not going to provide evidence for it", I assume that means they looked for evidence and couldn't find any. Lots of things are commonly known in a subgroup despite having no primary sources. That may not be the case here, but it's a better policy than taking things on faith in my opinion.