While I didn't go to an Ivy, that's clearly not true. Do you honestly think Google, Facebook, Microsoft, Goldman, law schools, medical schools, etc., are going to accept you if you have poor grades? Not everyone can count on "daddy".
It doesn't matter if all companies does this, it matter how many do.
Yes, at least for the tech companies. Grades are irrelevant at FB/MS/Google.
Again, I have no anecdotal experience, but I have a hard time believing that the new hires for those 3 companies are anything but students from top-tier colleges with near perfect grades. To be fair, I'm sure a couple of years of work experience and they probably don't care as much.