From my experience mentoring at FAANG is hit and miss. You may get a mentor assigned, yes. The thing is that this person is probably just an engineer who also needs to do their daily job. While mentoring you is a part of their daily job, it competes with tasks that are well defined and affect their evaluation. Fixing bugs is measurable and visible. Mentoring isn't, beyond showing up and sharing some information.

So yes, being proactive about finding a mentor is a spot on advice.