> If everything goes offline for one hour per year at the same time, then a person is blocked and unproductive for an hour per year. > On the other hand, if each service experiences the same hour per year of downtime but at different times, then the person is likely to be blocked for closer to 100 hours per year.

Putting Cloudflare in front of a site doesn't mean that site's backend suddenly never goes down. Availability will now be worse - you'll have Cloudflare outages* affecting all the sites they proxy for, along with individual site back-end failures which will of course still happen.

* which are still pretty rare