Comment by zootboy

It's not outdated, you just actually need to follow it. 3 copies of data in separate S3 buckets is ignoring the "2" in the 3-2-1 rule: 2 different mediums, and also the "1" rule: 1 copy offsite. In the cloud era, offsite means not on the same cloud provider. Different mediums ideally means a non-cloud provider (e.g. a NAS at your office under your control).