Yeah, if you work for Facebook on something Google wants, you can flunk 10 onsite interviews in a row... There was some blog post from a guy who flunked like 7 onsite interviews, year after year, before he got into Google...
Interesting. Never knew that, it seems like it's almost a normal part of the process to be told to "try again in 6 months".
From my own experience, this is not true!
"Out for good" is weird here. I interviewed with them more than a decade ago. They'd still consider that "signal"?
They might bring you in to get additional datapoint regardless.
They might, except that I have turned down their recruiters in the last 8 years or so.
IIRC this only applies for on-sites and not the phone screen.