I mean five nines is legitimately difficult to accomplish for a lot of problem spaces.

It's also like.... difficult to honestly and accurately measure. And account for whether or not you're getting lucky based on your underlying dependencies (servers, etc) not crashing as much as advertised, or if it's actually five nines. Or whether you've run it for a month and gotten <30s of measure downtime and declared victory, vs run it for three years with copious software updates.

I always assume most people claiming five nines are just not measuring it correctly, or have not exercised the full set of things that will go wrong over a long enough period of time (dc failures, network partitions, config errors, bad network switches that drop only UDP traffic on certain ports, erroneous ACL changes, bad software updates, etc etc)

Maybe they did it all correct though, in which case, yea, seems hard hitting to me.