Have you heard or seen the tag line "just sayin"?

What does it mean?

That question might be obvious to some, but I don’t get it.

I only started hearing people use “just sayin” about 6 months ago, and it jarred me.

If I’m correct, it claims a superiority to the speaker/writer. They are stating an opinion and marking it as unassailable. By adding this minute tag, they seem to think they can forego facts.

I really am puzzled by this cliche.