For starters, I find it odd that you claim that the recruiter gave you feedback, and on the technical skills of all things. If you reached the last round of interviews of a FAANG, that round does not focus on technical aspects and it's more focused on soft skills and personality traits that emerge during the interview. In fact, I know for a fact that they don't look at the solution at all, and look at the process that the candidate follows such as how he takes suggestions and how he attacks problems or how he adapts to changing requirements. Sure, there are technical questions, but they barely fill 30% of the interview time, and even then their main goal is to gather info on the candidate's personality traits.
With that in mind, it's easy to believe you bombed your interview if you are the type of person who opens a discussion on a public forum attacking your interviewer with accusations of being too incompetent to evaluate you and too immature and having no clue about how great you are and how awesome you did. Just from this post alone I was readily convinced I would hate to work with someone like you, and apparently so did your interviewers.
If you ask me, they've clearly dodged a bullet.