2. is not accurate. Managers don't have to hire weak people to satisfy the quota. People are rarely ever put into PIP due to performance. Most of the times it is political.
You might ask “why would an HM fire someone who is qualified to do the job?” The answer is that Amazon requires that someone must be fired. If you were an HM, who would you rather fire: an existing qualified tenured team member who already knows the ins-and-outs of your team and system, or a new qualified person who would require extensive training and time to get up to the level of the tenured employee? You’re going to pick the new person, even if they are qualified.