Your statement sounds much like the old “if you get caught doing $x at school it will go on your permanent record”. BigTech is so vast that unless you do something egregious it’s hard not to get hired back at the same one, let alone a competitor.

For every you that wouldn’t hire the parent posters, there are hundreds of managers that will.

No part of the hiring loop at major tech companies for ICs that I am aware of involves checking references. We definitely don’t do that as part of the loop. Our entire hiring process is based on how well you do in the interview.