It's not about losing a few kb here and there.

It's about losing entire data centers to massive natural disasters once in a century.

None of the big cloud providers have unrecoverably lost hosted data yet, despite sorting vast volumes, so this doesn't seem BS to me.

AWS lost data in Australia a few years ago due to a power outage I believe.

on EBS, not on S3. EBS has much lower durability guarantees

Not losing any data yet doesn't give justification for such absurd numbers

Those numbers probably aren't as absurd as you think. 16 9s is, I think 10 bytes lost per exabyte-year of data storage.

There's perhaps the additional asterisk of "and we haven't suffered a catastrophic event that entirely puts us out of business". (Which is maybe only terrorist attacks). Because then you're talking about losing data only when cosmic-ray bitflips happen simultaneously in data centers on different continents, which I'd expect doesn't happen too often.