I would personally always have an off-platform backup to fall back on, as protection against the platform going down, accidental damage to data or malicious damage to data. Snapshots in cold storage too.
Not a lawyer or anything, but my layman's understanding is that, you essentially are voluntarily opting-in to waiving liability when you sign up for AWS and accept the terms and conditions, and instead of liability, you agree to accept service credits if SLAs are not met.