> 1% is 3.5 days

I think that illustrates the author's point quite well. 99% uptime sounds good, but when you think about a 3+ day outage that doesn't sound very good. Imagine Facebook or TikTok being down for 3 days.

Of course most of the time it's not all one outage, but a bunch of short ones. Still, it might communicate the impact better, especially depending on the argument you're trying to win.